I'm all for mental health reform and being sensitive to people's internal struggles, but the minute someone expresses themselves with violence (even against inanimate objects), that's a hard limit in my opinion. Especially when it's premeditated like this; it's not like the guy accidentally punched a hole in the wall... he went into his car for a weapon, knowing full well that he was in uniform, being recorded in a highly visible space.
Besides, the better 'Robin Hood' move would have been to just walk up and lift the gate himself... aren't those things pretty easy to manipulate?