Investigators are working to break into the phone of the man who shot at former President Donald Trump at a Pennsylvania rally on Saturday. The shooting is being probed as an assassination attempt.

The FBI said in a statement that it had obtained the shooter’s phone “for examination.” Officials told reporters in a conference call on Sunday, as reported by The New York Times, that agents in Pennsylvania were unable to break into the phone. It’s been shipped to the FBI’s lab in Quantico, Virginia, where the FBI hopes to get past the phone’s password protection, the Times reported.

Investigators are still looking for insight into the motives of Thomas Matthew Crooks, a 20-year-old from Bethel Park, Pennsylvania, who they identified as the gunman. Kevin Rojek, the FBI special agent in charge in Pittsburgh, told the Times and other outlets that the agency has access to some of Crooks’ text messages, but they haven’t shed much light on his beliefs.

It’s not clear what brand of phone Crooks had, and the FBI did not immediately respond to The Verge’s request for comment. While law enforcement is often successful with breaking into suspects’ phones — either by serving a warrant to access a suspect’s iCloud backups or by using third-party phone cracking technology — it has also butted heads with tech companies over requests to bypass device encryption. In 2015, Apple refused to help the FBI bypass the encryption on the iPhone of a shooter in San Bernardino, California, claiming that in order to respond to the government’s request, Apple would necessarily have to write custom software that undermined the security of all iPhones. The FBI eventually managed to break into the phone with the help of an Australian security company.