an organ transplant or lung, breathing, or liver problems. (roger ) before i'd think of the stuff i might miss. but now with keytruda, we have hope. (avo) living longer is possible. it's tru. keytruda, from merck. ask your doctor about keytruda. next this thursday night, the urgent search for a serial shooting suspect in chicago. police releasing surveillance now of the masked gunman accused of killing two people in two days, targeting victims they believe at random, including a man simply walking his dogs. here's abc's alex perez tonight. >> reporter: tonight, chicago police on the hunt for this man, seen here, dressed all in black, his face hidden. calmly walking down the street moments before, according to police, he gunned down a man, randomly, in cold blood. six minutes later, police say another camera capturing the suspect running right after 73-year-old douglass watts, who was shot in the head, point-blank range while walking