By Tim Gaynor
PHOENIX (Reuters) - 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 Saturday.
The Arizona Republic newspaper said federal agents seized numerous computers and munitions from the Phoenix valley home where white supremacist Jason Todd "J.T." 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 U.S. 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's Phoenix field office, confirmed to Reuters 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 U.S. Border Guard group, a private-citizen militia in Arizona that advocated deadly force to stop illegal immigration over the border from Mexico.
A profile of Ready by the nonprofit Southern Poverty Law Center said he had attended neo-Nazi gatherings in Nebraska and Phoenix, and railed against Jews and "Negroid immigration" in white nationalist online forums.
He advocated deadly force to stop Mexicans from crossing into the United States illegally, and favored laying a minefield along the U.S. border, the center said.
Police identified the dead as Lisa Lynn Mederos, 47, who they said was Ready's girlfriend; Amber Nieve Mederos, 23; Jim Franklin Hiott, 24; and 15-month-old Lily Lynn Mederos, who was still alive at the scene but later died in a hospital.
(Reporting By Tim Gaynor; editing by Todd Eastham)