By retorting with gunfire, he's shown himself to be not of the Sanders ilk. Sanders did not advocate violence.

This man was a loser. He was "living out of a gym bag." He was a loner. He needed to see a shrink fast.

He was a lot of bad things, including a vile fanatic.

Unfortunately he also had access to a gun.

Fortunately he was a bad shot. It could have been worse.