The L.A. Police Department says 19-year-old Ivan Gallegos stabbed 27-year-old Xavier Cerf Monday night after he saw him breaking into his car in the rear parking lot of his fraternity's house.
Gascón said witnesses were consistent in their statements indicating Cerf claimed to have a gun when Gallegos confronted him.
When Cerf reached for his waistband, that's when Gallegos stabbed him, Gascón said.
Ultimately it appears Cerf did not have a gun but Gascón said it was clear Gallegos was in fear for his life.
"There is consistency in the assessment that the decedent indicated he had a gun," Gascón said. "Although he didn't have a gun. He did reach out for his waistband. When you look at the totality of the circumstances, it really indicates there was a reasonable belief, that Mr Gallegos believed his life was in danger."
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Gallegos was arrested on suspicion of murder after the fatal stabbing, but Gascón said after reviewing the evidence he would not bring any charges against him.
How events unfolded
Documents from the DA's office spell out a brief narrative of the incident compiled by investigators from multiple witness statements:
Monday night around 8 p.m. the alarm started going off on Gallegos' 2010 Mercedes Benz parked behind the frat house. Security video showed Cerf had broken into the car.
Gallegos and three others came out from the frat house to investigate. Gallegos armed himself with a knife - telling investigators later that was because the area was known to be dangerous. One of the other men with him was armed with a large stick.
When they approached Cerf and asked him to get out of the car, Cerf reportedly refused, claiming the car was his because it was "calling him" and "had his name."
But then he did start to get out of the car but claimed to be armed with a gun and reached for his waistband.
That's when Gallegos moved in, using his left hand to grab Cerf's hands to stop him from pulling out the supposed gun from his waistband.
With his right hand, he stabbed Cerf in the chest, investigators said in the report.
They continued to struggle and Cerf again reached for his waistband, the report says, and Gallegos stabbed him three more times and pulled Cerf out of the car. Cerf then released his grip and walked away, as Gallegos and the three other witnesses went back into the frat house and called police.
The other witnesses confirmed the story saying they heard Cerf claim to have a gun and reach for his waistband.
"The use of deadly force under these circumstances was both proportionate and objectively reasonable and would support a claim of perfect self-defense. Filing is rejected," the DA's document states.
Friends show support for Gallegos
Last month, USC's Annenberg Media published a profile of Gallegos describing him as an up-and-coming musical artist who is attending the Marshall School of Business.
Friends and family said Gallegos was too traumatized by the incident to speak to the media but he did ask about Cerf's family.
"We've come together as a community, all friends and family, to show support and love for Ivan," said Rafael Cardenas, a friend of Gallegos. "Ivan is an amazing individual. He's very gifted and talented. We really came here to bring justice for Ivan."