 Law enforcement then tried to get up, a local cop tried to get up on top of the roof to see him. That's when he turned, pointed the gun at the cop. The cop dropped down because he was kind of holding on with both hands on the edge of the roof line. And so he did not have the ability to pull his weapon. He drops down. Minutes later, he opens fire on the crowd. Bystanders also called police about his behavior. Pittsburgh NBC affiliate WPXI reported that law enforcement was alerted about 30 minutes before the first shot rang out.