Agent 47 is hidden out of view, 20 metres from the person he is about to shoot.
Agent 47 shoots the person with a sniper rifle 20 metres away.
Some random guard 15 meters away from Agent 47 sees the shooting, but cannot see Agent 47.
That random guard automatically puts Agent 47 into Combat mode because the guard is less than 20 meters away. If Agent 47 was say 25 metres away, he would run to the source of the shooting instead of going into combat mode.
Why does that guard put Agent 47 into combat mode when in close proximity? The Guard cannot see Agent 47, he is 15 metres away out of view behind walls.
Don’t put the guard in Combat mode just because he is within a certain distance, instead… put him in search mode and make the guard go to the area of Agent 47 to search for the shooter… this is a much more realistic approach.
Check if the guard can see Agent 47 first, then put it into Combat mode if the guard can see Agent 47.