REUTERS PHOENIX THE neo-Nazi founder of an anti-immigrant border militia was already the subject of an FBI domestic terrorism probe before he went on a shooting rampage and killed four people, officials and news reports said on Sunday.

The Arizona Republic newspaper said federal agents seized numerous computers and munitions from the Phoenix valley home where white supremacist Jason Todd “JT” Ready is believed to have killed his girlfriend and three others on Wednesday following a domestic dispute, before shooting himself. After the shooting, the FBI contacted local police in Gilbert and asked for their agents to be involved in the investigation, James Turgal, special agent in charge of the FBI’s Phoenix office, told the newspaper.

The FBI’s domestic-terrorism investigation dated to when Ready was a member of the neo-Nazi National Socialist Movement and continued into his activities with the US Border Guard border-vigilante group, the newspaper reported.

The probe was based on tips of criminal activity that Turgal declined to specify, but was unrelated to the shooting rampage on Wednesday, the newspaper reported.

Manuel Johnson, a spokesman for the FBI confirmed that Ready, was the subject of a federal domestic terrorism investigation prior to his death. But he declined to provide further details “due to the ongoing investigation.” After the shooting, authorities retrieved two handguns and a shotgun from the crime scene, as well as live military grenades that were removed by an Air Force bomb disposal team.

Ready, 39, founded the US Border Guard group that advocated deadly force to stop illegal immigration over the border from Mexico. A profile of Ready said he had attended neo-Nazi gatherings in Nebraska and Phoenix, and railed against Jews.