Trump shooting motive unknown after assassination attempt

The motive of the 20-year-old gunman who tried to assassinate former President Donald Trump remained unknown three days after the shooting at a campaign rally in western Pennsylvania.

Information analyzed from a phone belonging to the gunman, Thomas Crooks, has not helped the FBI determine what led him to fire a rifle multiple times at Trump and other rally attendees Saturday afternoon before he was killed by a Secret Service sniper, a senior law enforcement official told NBC News.

Authorities found more than a dozen guns were in a search of the Crooks family home.

Two suspected improvised explosive devices were found in Crooks’ car near the rally, while a third suspected IED was found at his home.

A joint intelligence bulletin issued by the FBI and Department of Homeland Security warned that extremists may conduct attacks in retaliation for the assassination attempt, a source told NBC News.

“The FBI and DHS remain concerned about the potential for follow-on or retaliatory acts of violence following this attack, particularly given that individuals in some online communities have threatened, encouraged, or referenced acts of violence in response to the attempted assassination,” the bulletin said, according to the source.

That same bulletin confirmed that Crooks purchased 50 rounds of ammunition at a store in his hometown of Bethel Park, Pennsylvania, on Saturday before he drove to the rally.

The FBI spoke to more than 100 witnesses, family members of Crooks and friends, rally attendees and other law enforcement officials in an effort to map out the gunman’s steps leading up to the shooting and determine what motivated him to do it.

Meanwhile Tuesday, the Secret Service, which is responsible for protecting Trump, continued to face strong criticism for not taking precautions that might have prevented Crooks from crawling onto a roof overlooking the rally site with his rifle and firing shots that injured the former president, killed one man and wounded two others.

The shooting occurred two days before the Republican National Convention kicked off in Milwaukee and formally nominated Trump as the GOP’s presidential candidate for the November election.

Local police alerted Trump’s Secret Service detail before the shooting that they were looking for a suspicious person in the area of the rally, a U.S. official told NBC News. That person was later identified as Crooks, who had been seen pacing and acting oddly near magnetometers at the event.

Secret Service Director Kimberly Cheatle told ABC News in an interview that the shooting “was unacceptable … and it’s something that shouldn’t happen again.”

“The buck stops with me,” Cheatle said. But she also said she would not resign over the incident.

In the interview,…