The July Fourth shooting suspect's legal firearms purchases following repeated police background checks have exposed deep flaws in the piecemeal state and federal systems intended to stop someone like him.

Robert "Bobby" Crimo III, 21, held a valid Illinois Firearm Owner's Identification Card at the time of the shooting that killed seven people and injured dozens more in Highland Park, an upscale Chicago suburb. And he legally purchased at least five guns, authorities said, including the Smith & Wesson M&P15 semiautomatic rifle that he's accused of using in the attack.

“Based on what we know, I'd say the system worked as it was designed – it's just not comprehensive,” said Harold Krent, a professor at the Chicago-Kent College of Law. “Neither the initial licensing system nor the red-flag process is designed for an open-ended inquiry into fitness for operating a firearm.”

In other words, Crimo simply slipped through the wide-open cracks of a system where no single authority – local police, state or federal regulators, or his parents, friends and online followers – prevented him from amassing an arsenal of weapons and hundreds of bullets.