This is based on my limited expertise and what I think would be reasonable tactics.
Scenario - I am in a crowded, indoor space (movie theater, night club, church, etc.) armed with my PPS and an assailant armed with a rifle has entered to inflict harm. Of course my first choice would be to exit the enclosed space ASAP, but for the sake of this discussion let's assume that is not a viable option.
The scene unfolds, the shooting begins...
Panic and chaos ensues, people are running in all directions for their lives.
Assumption 1 - as the panic unfolds, the shooter cannot keep all of the victims in view as they disperse in various directions. Perhaps the shooter experiences tunnel vision from the adrenaline rush...
Assumption 2 - no longer able to focus on individual victims as they disperse, the shooter fires into the crowd that is within a certain visual arc in front of them.
Tactic - blend in with the chaos while attempting to flank the assailant unnoticed. Engage assailant when no longer in their visual arc of attention and when a clear shot is presented.
I know this is an over-simplified description of an extremely chaotic, unpredictable scene (and much easier said than done), but if I'm forced to engage I would like to try to gain every advantage possible - and have some preconceived plan on how to do so. In a nutshell I would attempt to (1) blend in with the chaos while (2) maneuvering into a flanking position and (3) engage at the best opportunity presented. A few seconds to fire a few well-aimed shots...
If I'm able to avoid panic myself, this is my current thinking in how I would go about it. TIA for any input/discussion.