Jason Todd “J.T.” Ready allegedly killed his girlfriend and three others on Wednesday following a domestic dispute, before turning the gun on himself.
Authorities recovered two handguns and a shotgun from the crime scene along with live military grenades that had to be removed by Air Force personnel.
According to reports, the probe was based on tips of criminal activity that FBI agents declined to specify, merely stating they were unrelated to the shootings.
Ready was the founder of the U.S. Border Guard group, a citizen-run militia in Arizona that advocated deadly force to stop illegal immigration from Mexico. The group also backed laying a minefield along the U.S. border.
Despite the FBI’s interest in Ready, he was never arrested nor interrogated by police. The four victims included 47-year-old Lisa Lynn Mederos and her 15-month-old daughter Lily Lynn Mederos.