A Blind Spot and a Lost Trail: How the Gunman Got So Close to Trump

About an hour before a gunman let loose a volley of bullets that nearly assassinated a former president, the law enforcement contingent in Butler, Pa., was on the verge of a great policing success.

Among the thousands of people streaming in to cheer former President Donald J. Trump at a campaign rally on Saturday, local officers spotted one skinny young man acting oddly and notified other law enforcement. The Secret Service, too, was informed, through radio communication. The suspicious man did not appear to have a weapon.

Remarkably, law enforcement had found the right man — Thomas Matthew Crooks, a would-be assassin, though officers did not know that at the time. Then they lost track of him.

Twenty minutes before violence erupted, a sniper, from a distance, spotted Mr. Crooks again and took his picture.

As time slipped away, at least two local officers were pulled from traffic detail to help search for the man. But the Secret Service, the agency charged with protecting Mr. Trump, did not stop him from taking the stage. Eight minutes after Mr. Trump started to speak, Mr. Crooks fired off bullets that left the Republican presidential nominee bloodied and a rally visitor dead.