More details than what I just posted:
By 3 p.m. on Saturday, Thomas Matthew Crooks was at the security screening area for the Trump rally in Butler County, Pennsylvania. He first aroused suspicion when he passed through the magnetometers carrying a rangefinder, which looks similar to a small pair of binoculars and is used by hunters and target shooters to measure distances when setting up a long-range shot, according to a senior law enforcement official briefed on the investigation.
The rangefinder would not have prevented Crooks from getting through the security screening point,
but it did attract the attention of security personnel who kept an eye on him until he left the secure area.
-Investigators are unsure of where Crooks went after he left the screening area but the
working theory is that he went to his car to retrieve the rifle.
-Crooks
gained access to that rooftop by climbing on top of the building’s air conditioning system and hoisting himself up, according to a senior federal law enforcement official briefed on the investigation.
-Additionally, after a search of his residence, investigators
discovered another bulletproof vest, another remote-controlled explosive device and a 3D printer, according to multiple law enforcement sources.