first tonight, hunter biden's gun trial begins. the first trial of a child of a sitting president. the first lady there in that courtroom. also developing, president biden preparing a new executive order, a crackdown on the mexico border. it would shut down the border immediately to asylum seekers if daily migrant numbers hit 2,500. and what we're learning about this. in new york city tonight, those two nypd officers shot and wounded. chasing a robbery suspect. one shot in the chest, saved by his bulletproof vest. what authorities have now revealed about the suspect. this major heat wave already building tonight. temperatures well into the triple digits across several states. and the wildfire burning in california. the swimmer attacked by a shark off the coast. bitten on the chest, arm, and hand. witnesses on how the swimmer survived. israel's war with hamas. tonight, the israeli military now confirming the deaths of four more hostages in gaza. here in the u.s. tonight, the heated testimony on the hill. dr. anthony fauci defending his handling of the covid pandemic. and fauci turning deeply emotional when revealing the death threats against his family. the accused serial killer outside new york city, the new report tonight indicating new charges could now be coming, after this newest search of his home. and after 41 seasons of "wheel of fortune," the final week for pat sajak. tonight here, the interview with sajak by someone he knows very well. and what he says when asked, could you have kept on going? >> announcer: from abc news world headquarters in new york, this is "world news tonight" with david muir. >> david: good evening, and it's great to start another week with you all at home. we do begin tonight with breaking news on the u.s./mexico border. what president biden now plans to do. also, two nypd officers shot and wounded. we have news coming in on the suspect. but we start tonight with the trial of hunter biden on felony gun charges. the first child of a sitting president ever to go to trial. 12 jurors and four alternates were seated today. hunter biden arriving at federal court in wilmington, delaware, along with his wife, melissa cohen-biden. first lady dr. jill biden there to show her support. his father, the president, tonight sending his boundless love to his son. hunter biden is accused of lying about his drug use on a federal form when he bought a handgun in 2018. for years, hunter biden has been open about his drug addiction and his fight to beat it. tonight, prosecutors now plan to use hunter biden's own words against him. abc's terry moran leading us off at the courthouse tonight. >> reporter: hunter biden walked hand-in-hand with his wife, melissa, into the federal courthouse in wilmington, delaware, this morning to stand trial on charges of violating federal gun laws. minutes later, first lady jill biden made her way into court on her 73rd birthday. the case marks the first time in american history that the child of a sitting president has gone on trial. hunter biden faces three felony gun charges in what prosecutors are calling a simple case. they allege that he lied about his drug abuse on this federal form back in october 2018, when he bought a colt cobra .38 special handgun. for years, the president's son has been open about his fight with drug addiction. >> that i have made mistakes in my life, and wasted opportunities and privileges i was afforded. for that, i'm responsible. >> reporter: now prosecutors plan to use his words against him in court, including excerpts from his 2021 memoir "beautiful things," where he came clean about his addiction, and his text messages. this one allegedly sent just two days after buying that firearm. "i was sleeping on a car smoking crack on 4th street and rodney." hunter biden's lawyers have argued in court documents that that form is confusing, and so their client did not knowingly lie. last year, a plea deal in this case fell apart under tough questioning by the same judge who will now preside at trial. the jury selected today, six men and six women, including a man whose father died by gun violence and whose brother was sentenced to prison for drug crimes. a woman who grew up in a hunting family with guns and whose best friend died from a drug overdose. and a man who has owned six guns in his life and told the judge, "i believe the second amendment is very important." earlier today, president biden released a statement standing by his only surviving son, saying in part, "i have boundless love for my son." in court, hunter biden has been an active participant, conferring frequently with his lawyers during jury selection. and he's been an attentive son, checking in on the first lady. at one point during a break, embracing her with visible emotion. opening statements in this case begin tomorrow morning. david? >> david: terry moran leading us off here tonight. terry, thank you. meanwhile, there is a developing headline tonight involving the u.s./mexico border. this evening, sources now say president biden is preparing to take tough executive action on immigration, including shutting the border when the number of asylum seekers reaches 2,500. it would trigger an immediate shutdown. it comes tonight as the new president of mexico, their first woman president, a physicist and engineer, has already signaled she will work with the u.s. on immigration. rachel scott at the white house. >> reporter: tonight, president biden preparing to take his most aggressive action on immigration yet, with plans to issue an executive order to effectively shut down the border to asylum seekers when migrant crossings surge. sources tell abc news when daily encounters reach 2,500 between ports of entry, asylum seekers would be turned away. the move could have an immediate impact. migrant crossings have averaged 3,500 a day in recent weeks. the president, keenly aware that immigration is a top issue for voters, has been weighing how he can act alone, after donald trump urged republicans to block a bipartisan deal their own party negotiated. >> there's no guarantee that i have that power all by myself without legislation. and some have suggested i should just go ahead and try it. >> reporter: the u.s. has seen a record 6.4 million illegal border crossings during the biden administration. officials say the numbers have dipped in recent months because mexico was cracking down on their side of the border. and the u.s. will soon have a new partner. mexico tonight electing its first woman and first jewish president, claudia sheinbaum, the former mayor of mexico city, a physicist with a doctorate in energy engineering who won the nobel peace prize. sheinbaum is vowing to continue the policies of outgoing president lopez obrador, working to control the flow of migrants. david, and back to that executive order, this could have an immediate impact for those who are seeking asylum. the number of migrant encounters at the border already far exceeds that threshold. the white house and the biden administration fully aware this will likely be challenged in court. david? >> david: rachel scott with the developing headline from the white house tonight. thank you, rachel. here in new york city tonight, news on two nypd officers shot and wounded while chasing a robbery suspect. one shot in the chest, saved by his bulletproof vest. and what authorities have now revealed about the suspect, a migrant from venezuela. here's our senior investigative correspondent aaron katersky. >> reporter: tonight, these two young new york city police officers are out of the hospital and lucky to be alive after they were shot by a migrant wanted for robbery in queens. >> this is a bullet hole. because of this vest, a young police officer is going home. >> reporter: officers richard yarusso and christopher abreu, both 26, were shot just before 2:00 a.m. while searching for suspects in a string of robberies by thieves on scooters. >> they observe a male suspect drive a moped the wrong way and attempted to pull him over. the suspect then fled on foot. >> reporter: police sources told abc news the officers wrestled the suspect to the ground. they were all within inches of one another when the suspect pulled a gun out of a fanny pack and fired. >> one is confirmed shot in the leg and one in the vest. we have one perp that's shot. >> reporter: officer yarusso trying to stop his partner from bleeding. >> the one police officer shot in the vest was more concerned about his partner, saving his life, getting a tourniquet. >> reporter: detectives recovered this illegal handgun at the scene and arrested bernardo mata, a 19-year-old from venezuela, who entered the u.s. illegally a year ago and had been living in a migrant shelter. david, this suspect is wanted in connection with multiple robberies in queens. he was shot in the leg in the altercation with the officers. tonight, he's in the hospital awaiting charges. david? >> david: aaron katersky here in new york. thanks, aaron. we turn now to the major heat wave building tonight. several states with triple digit heat already. in fact, 25 million americans on alert for dangerous heat, as california tonight already battles a wildfire there. the corral fire east of san francisco racing across more than 20 square miles in the last 48 hours alone. part of interstate 580 shut down for a time. families forced to evacuate. tonight, crews battling the flames and the temperatures. mola lenghi on the fire lines for us. >> reporter: tonight, a new threat for the west, scorching heat. 475 firefighters already battling california's first major wildfire of the year. the dry grass quickly going up near the town of tracy. the corral fire incinerating more than 20 square miles east of san francisco in the last 48 hours. >> the winds were fierce, 30 to 40-mile-an-hour sustained winds and 60-mile-an-hour gusts. people were saying they couldn't even stand up in those high winds. >> reporter: two firefighters sustaining burns when the erratic winds changed direction, expected to be okay. >> first time i walked over here, and it's very hard to look at. it still is. >> reporter: travis curtiss' parents evacuating as flames closed in on his childhood home, now destroyed by the fire. >> they left with the clothes on their back. and so -- >> reporter: and came home to nothing. >> came home to nothing. >> reporter: the start of the fire not far from the explosives testing facility belonging to the famed lawrence livermore national lab. authorities warning that fire season is now a year-round event. >> usually we see the more intense fire activity in july, august, september. so, we just want everybody to be prepared. >> reporter: well, david, the national weather service issuing an excessive heat warning for millions here in california starting tomorrow, with temperatures expected to hit up to 108 degrees, prompting some real concerns about the heat, not just here, but throughout the west, david. >> david: makes those fire fighters and their job even more difficult. mola, thank you for that tonight. we turn now to the swimmer attacked by a shark off the california coast north of san diego, bit on the chest, arm, and hand. witnesses tonight on how the swimmer survived this, and it turns out, an emergency room physician happened to be nearby, and was able to help. kayna whitworth in california tonight. >> reporter: tonight, a popular beach just outside of san diego closed, and residents on high alert, after a shark attacked a man while swimming with a group 100 yards from shore. >> i heard this -- the scream. and you kind of know when it's a real scream, like, okay, that's -- that's not a -- that's not okay. >> reporter: it was around 9:00 a.m. when authorities say he encountered what is believed to be a juvenile white shark. despite sustaining significant injuries to his chest, arm, and hand, the 46-year-old managed to break free by punching the shark. kevin barrett, part of that group, just feet away. >> when i got to him, it was -- it was pretty evident that he was, you know, in major distress. it was a little scary because you don't know what you're swimming into. >> reporter: morning beachgoers, an e.r. doctor, and life guards jumping into action. caleb, who regularly trains at the beach, was taken to a local hospital and is now in stable condition. researchers at cal state long beach immediately taking water samples and using a drone to try and locate the shark, but they were unsuccessful. past studies have shown 97% of the time people were in the water at an aggregation site, a white shark was nearby. and david, years of research indicate sharks in the area are anywhere from 4 1/2 to 9 feet long. and while bites are rare, they encourage everyone to use caution, especially when visibility is low. david? >> david: kayna whitworth tonight. thank you, kayna. now, to the israel-hamas war, and tonight, the israeli military confirming four more hostages have died while being held by hamas. three of them had been seen pleading for their lives in a video put out by hamas in december. marcus moore is in israel tonight. >> reporter: tonight, the israeli military acknowledging, quote, difficult questions will be asked, after the deaths of four more hostages being held by hamas in gaza. according to the idf, new intelligence confirms chaim peri, yoram metzger, amiram cooper, and nadav popplewell were killed several months ago. >> we assess that the four of them were killed while together in the area of khan younis during our operation there against hamas. >> reporter: the idf has not said how they died. back in december, peri appeared in this hamas video, pleading, "don't abandon us." a lifelong peace activist, peri surrendered to hamas militants to save his wife, who was hiding in their safe room. we spoke with their son, lior, shortly after peri's abduction. >> ever since he finished being a soldier, he became a strongly -- a strong peace activist because he said, it's very clear for me, very, very clear, that peace is the only way. >> reporter: peri's family tonight blasting the israeli government for not doing more to free the hostages, saying in a statement, "he could have been saved, he should have been saved." adding, "there will be no forgiveness for any further abandonment." this comes just days after president biden's announcement of a new ceasefire proposal. but prime minister benjamin netanyahu today insisting there will be no permanent truce until hamas is destroyed. david, the terrible news on those hostages comes as pressure mounts on both sides to agree to an immediate ceasefire. a state department spokesman said the only thing standing in the way is hamas. david? >> david: marcus moore in israel. thanks, marcus. back here in the u.s. tonight, and to the fireworks on capitol hill. dr. anthony fauci facing hostile questioning about the pandemic. and fauci today growing deeply emotional while revealing the threats against his family. here's abc's elizabeth shulze. >> reporter: tonight, in a contentious hearing on capitol hill, dr. anthony fauci choking up, as he described death threats against his family. >> it is much more troublesome, because they've involved my wife and my three daughters. >> at this moment, how do you feel? >> terrible. >> reporter: during the nearly four-hour hearing, fauci defending his record as the face of the nation's pandemic response, facing hostile questions over policies like social distancing and masks. >> when you and your agency made mistakes, dr. fauci, what happened? we all need to be held accountable. sometimes it's as simple as saying, we were wrong. >> reporter: but fauci defiant, rejecting unfounded gop accusations he helped fund research that caused the covid pandemic and covered up a theory the virus may have originated in a lab in china. >> none of us can know everything that's going on in china or in wuhan or what have you, and that's the reason why i say today, and i've said it to t.i., i keep an open mind as to what the origin is. >> reporter: david, house democrats investigating the pandemic say they've gone through hundreds of thousands of documents over the past 15 months. none of them provide evidence that fauci covered up the so-called lab leak theory. >> david: elizabeth schulze on the hill for us. elizabeth, thank you. some alarm for a time today when the new york stock exchange now blaming a technical glitch for an interruption in trading today. up to 40 stocks were affected, after incorrect prices were listed, including warren buffett's berkshire hathaway, that at one point showed a 99.9% drop. they're connecting the glitch now to an s.e.c. rule change that requires investors to settle their stock purchases in one day, rather than two. when we come back here tonight, outside new york city, the new headline at this hour about the accused serial killer after this newest search of his home. also, the longtime congresswoman revealing her battle with pancreatic cancer tonight. and later here, pat sajak on his final week on "wheel" after 41 seasons, and what he's saying now about whether he could have kept going. if you have chronic kidney disease you can reduce the risk of kidney failure with farxiga. because there are places you'd like to be. farxiga can cause serious side effects, including ketoacidosis that may be fatal, dehydration, urinary tract, or genital yeast infections, and low blood sugar. a rare, life-threatening bacterial infection in the skin of the perineum could occur. stop taking farxiga and call your doctor right away if you have symptoms of this infection, an allergic reaction, or ketoacidosis. 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