in march, ten people, including a police officer, were killed after a lone gunman opened fire inside king soopers store in boulder, colorado. >> i have been involved with this for 34 years, and i've never seen anything like it. >> reporter: law enforcement sources tell us that investigators are looking into whether this was a case of workplace violence, and whether the suspect, who is now deceased, was a disgruntled employee. ironically, the fire and police personnel who showed up on this scene today had just completed active shooter training. margaret. >> brennan: frightening. thank you, jeff. turning now to the covid pandemic. the pfizer booster shot is getting one step closer to a green light from the c.d.c., for americans 65 and older, and younger people who are at higher risk of severe infection. late today, another key panel recommended a third dose. cbs's omar villafranca reports. >> the motion passes.