Three minutes is a LOT of time when someone is shooting unarmed people.
My Army training included an exercise demonstrating the power of ambush. My team of a half dozen ambushers took on two vehicles carrying unprepared soldiers. None of them was even able to return fire and probably none would have survived an actual attack. It is EXACTLY like shooting fish in a barrel.
Our mock attack lasted about fifteen seconds, just long enough to empty a twenty round magazine with aimed fire.
Get a clock with a second hand and see how many times you can say "bang" in three minutes. Even if you allow a full two seconds between shots, that is still 90 shots. You could kill ten, wound forty, and still miss almost half the time.