then female guard says "central called for help in 8 block", so then you hear a muffled "come on lets go" from unnamed guard, more running footsteps, and then Mark yells LOCKDOWN after. So I don't think someone's left out.
True, it just seems that the other two unnamed guards wouldn't have enough time to get through either door that's controlled by Central. Unless those doors were already unlocked, the two would have had to get Central to open them.

The timing of those guards getting out of T-Block in the 12 seconds after locking the gang down is what's itching at me. I know, I know. It's fiction.