Arizona vigilante Jason Todd "J.T." Ready's final act might have been his most horrific, say police.

Police have identified the former Marine with ties to neo-Nazi and anti-immigrant groups as one of the five people killed in a shooting spree Wednesday in Gilbert, Ariz., a Phoenix suburb, according to the Associated Press.

It also appears that Ready, who was running for sheriff in Arizona's Pinal County, killed four people, including a 15-month-old baby girl, her mother and grandmother, before he turned the gun on himself, reports the (Ariz.) Republic.

Ready was the founder of U.S. Border Guard, a prominent anti-illegal immigration organizations, the newspaper reported. He also had belonged to the National Socialist Movement, which espouses White-supremacist theories. Although the newspaper reported that he also was a member of the Minutemen Project, Jim Gilchrist, the founder of the California Minutemen Project, denied Ready was ever a member.

Besides Ready, police identified the shooting victims as 16-month-old Lily Lynn Mederos, 23-year-old Amber Nieve Mederos, 47-year-old Lisa Lynn Mederos and 24-year-old Jim Franklin Hiott.

Lisa Mederos was identified as Ready's girlfriend and Amber and Lily were her daughter and granddaughter.

FBI agents and, because of weapons found at the scene, the bureau's terrorism task force were at the scene assisting local police officials with their investigation, reports Phoenix TV station KPHO. Police say they believe the incident was domestic violence-related, according AP.