FBI specialists gained access to Thomas Matthew Crooks’s phone and were analyzing it as part of an investigation into the attempted assassination of former President Donald Trump, the bureau announced Monday.

The FBI said its investigation into the shooting at Trump’s campaign rally in Butler, Pennsylvania, was still in an early stage as agents continue to search for answers about Crooks, the 20-year-old who authorities say opened fire on rallygoers, killing one and critically injuring two.