 They're going to have to look at how they assess perimeters. Now, outdoor, indoor, it can differ. Metal detectors. Snipers killed the shooter within seconds and were able to rush Trump off the stage. But firefighter Corey Capitore was killed and two others were critically injured. Investigators have learned Crooks used a semi-automatic rifle and got off eight shots. Police also found suspicious canisters and containers in his car as they worked to find a motive.