Shooter tried to buy tracer rounds Paddock tried to buy tracer ammunition at a gun show in the Phoenix area in recent weeks, a law enforcement official briefed on the investigation tells CNN. Paddock bought other ammunition at the show, but he couldn't obtain the tracer ammunition -- bullets with a pyrotechnic charge that, when the round is fired, leaves an illuminated trace of its path -- because the vendor didn't have any to sell, the official said.