GILBERT, Ariz. - Police said Thursday that they believe a Marine veteran with ties to neo-Nazi and Minutemen groups shot four people and then took his own life in a suburban Phoenix home.

Gilbert police spokesman Sgt. Bill Balafas said that police believe Jason Todd Ready, 39, was the gunman in Wednesday's shootings in a home in Gilbert.

Ready lived in the home with a woman who was among the dead. In addition to Ready's girlfriend, the dead include the woman's daughter and granddaughter and the daughter's boyfriend, according to media reports.

Ready was known in Arizona for organizing a militia with the goal of finding illegal immigrants and drug smugglers. Known as "J.T.," Ready led an outfit known as the U.S. Border Guard that dressed in military fatigues and body armor and carried assault rifles during patrols for illegal immigrants in the desert south of Phoenix.

Police identified the others killed as 15-month-old Lily Lynn Mederos; 23-year-old Amber Nieve Mederos; 47-year-old Lisa Lynn Mederos and 24-year-old Jim Franklin Hiott.

Balafas has said that all the evidence points to the shooting being related to domestic violence. But he said investigators aren't sure what triggered the shooting.

Officers have recovered two handguns and a shotgun from the home, but believe only a handgun was used, Balafas said. The gun Ready commonly was pictured carrying on desert patrols, a military-style assault rifle, wasn't in the house.

The shootings occurred in a subdivision filled with stucco homes with red-tile roofs.

Members of the federal Joint Terrorism Task Force and FBI agents removed what Balafas said were military-grade ordnance, munitions and two barrels of chemicals found behind the home. Phoenix FBI spokesman Manuel Johnson said agents would help Gilbert police investigate the source of the munitions and give other support.

Ready and Hiott were found dead outside the home, and the bodies of two women were inside. The toddler was found inside the home showing signs of life, but later died at a hospital.

A teenager in the house heard arguing followed by gunshots, Balafas said. She came out of a back room and found the bodies.

Officers had been called to the home previously for domestic disputes, Balafas said.