Well, apparently things work different in PRO mode.
For example, if I take out a security camera, a nearby guard will come to investigate.
Doing the exact same thing in regular mode, the guard is deaf as a stump. He never moves.
Even if I keep shooting at it.
Although he will respond to a vehicle being shot at.
I think this is the way it was intended, that the guards or NPC’s would be more sensitive to noise
when playing PRO mode, which would make sense.
Also when firing at the feet of an NPC, they stop to look, but if they see where the shot came from,
you get the bullet impact notice and they come after you.
This is probably no new to anyone but this is what I found.