The stand-off began at 8:40 Sunday night at a home on Habbitts Court off Senter Road after reports of shots fired.
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On Monday, SJPD posted an update to Facebook.
Sergeant Enrique Garcia explains the gunman's wife, daughter and niece were able to escape, unharmed. However, four other relatives and the gunman remained inside the home.
ABC7 News cameras were rolling as a group of people, who were visibly distraught, walked silently along Habbitts Court on Monday afternoon.
The group was embraced by neighbors living a few doors down from the murder scene.
Sgt. Garcia explained two victims were found in the front room with gunshot wounds. The pair was taken to the hospital, where they died.
Two other victims and the gunman were found dead after an hours-long stand-off which carried over into the early morning hours on Monday.
Police say they found the gunman in the side-yard, with a self-inflicted gunshot wound.
RELATED: Here's what we know about the San Jose standoff, shooting at a home on Habbitts Court that left five people dead
In total, three women and one male victim were killed, the suspect also died.
One neighbor who didn't want his face on-camera explained hearing about six shots coming from next-door. He says he, his wife and their five-year-old son hid in their master bedroom.
Moments later, he said the gunman's wife was inside their home.
"The wife jumped the fence and ran into my house and she locked the door in my kids' room," the neighbor said.
Police confirmed there was no documented history of domestic violence between the suspect and his relatives. However, questions remain about the man's motive.
"Detectives are not certain what caused the suspect to shoot his family members," Sgt. Garcia said in an SJPD Facebook update.
Monday afternoon, a man and woman returned to the scene and brought cleaning supplies into the home.
Sunday's quadruple murder-suicide marks the South Bay's deadliest shooting since March 2009.
"You can imagine, it must have been terrible for people being inside of a residence and a gunman opening up," Sgt. Garcia told ABC7 News. "And you're helpless and you can't do anything about it."
As of Monday night, the gunman's motive was still undetermined.