Investigations continue into the suspected gunman in Saturday’s failed assassination attempt against Donald Trump at a rally in Butler, Pennsylvania. The FBI is analyzing 20-year-old Thomas Matthew Crooks’s cellphone, though no apparent motive has yet to emerge. Crooks was a nursing home employee who had registered to vote as a Republican, though his acquaintances say he was fairly quiet with no overt political leanings. Federal investigators believe he acted alone, but they say they are still exploring all avenues.

Meanwhile, congressional Republicans have called on the Secret Service director, Kimberly Cheatle, to testify about apparent failures ahead of, and in response to, the incident. Cheatle has rejected calls to resign.

Video emerged Monday of witnesses warning law enforcement of the gunman two minutes before he began shooting from the roof of a nearby building. A local NBC affiliate reports the shooter was spotted by law enforcement nearly 30 minutes before he opened fire.