Trump shooting investigation continues as new details emerge about assassination attempt

An investigation is underway into the assassination attempt on former President Donald Trump, who appeared at the Republican National Convention in Milwaukee on Monday night — the first time he was seen in public since he was shot and wounded at his campaign rally in Pennsylvania.

The convention crowd cheered Trump, whose the ear was bandaged after being hit by a bullet on Saturday.

Details are beginning to emerge about the moments leading up to the shooting. People alerted law enforcement to the gunman’s presence on the roof of a building about 400 feet from the scene at least two minutes before the first shot was fired at Trump, video reviewed by CBS News shows.

A local law enforcement officer with direct knowledge of the incident told CBS News that three snipers were stationed inside the building the shooter used for his attack. The plan for the operation called for them to be stationed inside the building and watch the gathering through windows.

One of the snipers inside saw the shooter, Thomas Matthew Crooksoutside and looking toward the roof, observing the building and disappearing, according to the officer. Crooks returned, sat down and looked at his phone. At that point, one of the snipers took a photo of him. Crooks pulled out a rangefinder and the sniper radioed the command post. Crooks disappeared again, then returned a third time with a backpack. The snipers called to say he had a backpack and was walking toward the back of the building.

Officers believe Crooks may have used an air conditioner to get onto the roof. By the time other officers arrived, he had climbed onto the roof and was above and behind the snipers inside the building, the officer said.

Two other officers who heard the sniper’s call tried to climb onto the roof. State police began rushing to the scene, but by then a Secret Service sniper had already killed Crooks, the officer said.

The FBI is investigating whether the shooter was a politically motivated homegrown violent extremist, and investigators are still combing through his background. Justice Department officials told reporters that investigators have the shooter’s phone and are examining it at the FBI’s lab in Quantico, Virginia.