A ninth body has now been recovered at the scene of the Christmas Eve shootings in Los Angeles.
A man dressed as Santa Claus burst into a party, hosted by the parents of his ex-wife, on Wednesday and opened fire on those present.
The body of Bruce Pardo, 45, was later found with self-inflicted gunshot wounds early on Christmas morning.
Mr Pardo had entered the home in a residential neighborhood in Covina, 37km east of Los Angeles, just before midnight on Christmas Eve.
An eight-year-old girl who answered the door was shot in the face but survived before Mr Pardo stormed into the home and began spraying the occupants with bullets with a semi-automatic handgun.
After partygoers fled the scene, he torched the house with a home-made incendiary device before leaving.
A rented car parked outside the property was discovered to be loaded with 300 rounds of ammunition and a pipe bomb.
The car burst into flames as bomb disposal experts moved in, reports said.
Mr Pardo was found dead from a single gunshot to the head at his home in Sylmar, approximately 40km away, a few hours later.
Police had received a series of emergency calls alerting them to the initial incident, and when they arrived, the house was engulfed in flames and guests were running out.
Neighbours reported hearing a loud explosion before the blaze erupted.
Two girls, including the eight-year-old who answered the door, were taken to hospital with gunshot wounds and a 13-year-old girl was treated for injuries that were not life-threatening.
After the fire was put out, rescuers found three bodies in the basement.
Police are searching Mr Pardo's home for clues to the former aerospace engineer's rampage.
