Chalk one up for the good guys!
The last shots he fired were with the guy on the ground, still facing him. Shooter never left the building.
If the idea is to stop a threat, and the guys you've identified as being the threat are still alive and in your close proximity, then they're still a threat. Look closely at :50-:53 in the video. If that dude is facing me, I'm shooting until I'm empty, then loading another mag and shooting until he's dead or disappeared.
+1, they are still a threat as long as they are armed. He was in the back and may have saved lives by following them to the door. If he did not follow them maybe they would have taken some of the people at the front hostage or or shot them.