The scenario:
You are in a shopping area.
You are NOT close to an exit or solid barrier.

You hear the sound of a round being chambered behind you.

As you turn to see the threat, you notice an Armed Citizen Already drawing a handgun to stop the potential shooter..

You also notice someone pulling out a cellphone.

Time Freezes:

Do you;

Scream at the Armed Citizen to put his gun away and wait for the police?

Or do you throw out a quick Prayer the ARMED Citizen does not miss?

Keep in mind, the Armed Citizen can have a round off BEFORE the other person can press 911.