Gilbert police said suspected gunman J.T. Ready, who was running for Pinal County sheriff, went on a shooting spree in the home Wednesday, killing 47-year-old Lisa Mederos; her daughter, 23-year-old Amber Mederos; Amber's boyfriend Jim Hiott, 24; and the couple's 15-month-old daughter, Lilly, The Arizona Republic reported Thursday.
Investigators believe Ready, whose relationship to the family was not reported, then turned the gun on himself.
"Our investigation is directing us to murder-suicide," said Sgt. Bill Balafas. "There is no indication of outside players at all."
A woman inside the house who survived the attack said she heard arguing and gunshots, though police are still searching for a motive.
Balafas said the family living at the house had called police several times in the past for reports of domestic violence, though he could not verify if Ready was involved in those incidents.
Celebrity Couples of 2014 [PHOTOS]