Less than 24 hours after a bullet whizzed across a Utah college campus and claimed the life of conservative activist Charlie Kirk, polarizing figures from across the political spectrum swiftly canceled public events. AdvertisementKirk’s killing comes amid a spate of attacks on high-profile political figures — including two assassination attempts on President Trump — that security experts say will change the way large-scale political events are held, with open-air venues increasingly seen as risky. Kirk was being protected by roughly a half-dozen Utah Valley University police officers and a handful of private security guards Wednesday, according to campus security officials. Typically, security professionals seek to create three “rings of protection” around the focus of a public event, according to Kent Moyer, founder of World Protection Group, an international security firm. “If you’re going to do an outdoor event you better make sure you have some kind of surveillance of rooftops,” Levin said.