Are you supposed to shoot your own guys?
No. But the guy who got shot in the video isnt on the team of the guy who shot him. He was the enemy. Your teammates will have their gamertags/screennames and ranks constantly floating over their heads. You enemies will not, except when you have aimed your weapon at him. Notice that the guy staring at the poster did NOT have his name floating above his head except when the shooter had his gun aimed at the guy.