Actually, that's not true. The guy only had an anti-Trump sign. Someone in the crowd yelled,"Gun!". He didn't have a weapon.
You need to do some more reading, FRiend. Based on his Facebook page, he was clearly a Clinton plant. He also shows up on the Wikileaks' George Soros funded list.
Facts:
He had already voted.
He voted for Hillary Clinton.
He was in the front row at a Trump rally.
He had bad intentions, which is the only reason he was there!