The sister of a federal officer allegedly killed by a member of a domestic extremist movement is suing Facebook, charging that the platform’s recommendation system played a part in the radicalization of the people who are accused of carrying out the shooting.

Federal law enforcement officials allege that Dave Patrick Underwood, a Department of Homeland Security officer, was shot and killed in a drive-by shooting by Steven Carrillo in May 2020 while Underwood was standing watch outside the Ronald V. Dellums Federal Building in Oakland, California. One week later, Carrillo was arrested after an alleged shootout with Santa Cruz County police officers that left Santa Cruz Sheriff’s Sgt. Damon Gutzwiller dead.

According to Facebook messages obtained by federal prosecutors, Carrillo met Robert Alvin Justus Jr., the driver of the vehicle from which he is alleged to have opened fire on Underwood, through Facebook groups for the Boogaloo movement, which first gained traction in early 2020 and espoused extreme anti-government views, NBC News reports. 

Both Carrillo and Justus have pleaded not guilty and are awaiting trial. Carrillo’s lawyer also said his client had suffered a traumatic brain injury before the shootings and suffered personal family loss.

Underwood’s sister, Angela Underwood Jacobs, filed a lawsuit in Alameda County Court on Thursday morning, alleging “extreme pain and suffering endured by Dave Patrick Underwood from the time of the shooting until the time of his death” and “for his wrongful death.”