SIMI VALLEY (CBSLA) — Police say a man who had been living in his uncle’s Simi Valley home killed his mother after a dispute, before turning the gun on his uncle’s dog and himself.

(credit: CBS)

Police say the homeowner returned to the home in the 500 block of Fairfield Road just before 7 p.m. Thursday and found his sister-in-law, 58-year-old Esperanza Guadalupe Cullen of Las Vegas, dead and covered in blood.

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“She wasn’t supposed to be there,” an unidentified neighbor said the homeowner had told him. “‘I don’t know. I don’t know. I’m just in shock.'”

The homeowner also found words scrawled on a wall saying there was a bomb in the house, prompting the evacuations of dozens of homes from the gated community. Ventura County’s SWAT team and bomb squad were called in, and authorities searched the area with a drone.

When police determined there was no bomb, they found two more bodies on the second floor – a man later identified as Michael Cullen and a dog, both who had been shot to death.

Cullen died of an apparent self-inflicted gunshot wound inside his bedroom, investigators say.

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Michael and Esperanza Cullen (Photo via Simi Valley PD)

At this point, investigators say it appears that Esperanza Cullen and Michael Cullen had a dispute inside the home.

“The couple that owns the house, and they were both at work from what I understand — the owner is just the nicest man, like I said. Loves his dog, walks his dog every day,” neighbor Maxine Evans said.

The man who police say killed himself was the homeowner’s nephew, and had lived in the home for the past two years, according to neighbors.

Neighbors said, in hindsight, they did hear the gunshots — but the sound did not register as a shooting.

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“Gated security or not,” a neighbor said with a shrug, “I don’t feel that safe.”