Firstly, I was wrong to say only two commandos descended.
I was wathching the timer and missed the others.

The microphone used for the commentary was very low sensitivity.
It does not pick up voices a few feet away. You barely hear the helicopters.
The gunfire is as far away as the helicopter but is clearly heard.

The narrator speaks of unspecified, out of sight injuries, never of incoming fire. Just the cannisters.