Something seemed deeply wrong with David Zapata.
Claudia Montes, his ex-girlfriend and mother of his son, knew it. So did his friends, who sent him Facebook messages expressing his concern.
Zapata had stopped answering calls. He did not respond when Montes asked him questions. He sometimes thought she had said something when she hadn’t opened her mouth at all. She said he believed she had solved the 2008 murder of her brother, whom she never met. And he would speak of himself in the first person plural.
Images of the suspect from two stabbings in Los Angeles on March 3 were released.
(Los Angeles Police Department)
“We know what you’re doing,” he would tell Montes, speaking only for himself, she said.
“For a long time I would say… ‘Something’s wrong with David. It doesn’t seem right,’” Montes said.
Police say the disruptive behavior culminated Friday, when a 17-year-old honor student was stabbed to death outside King Torta on Valley Boulevard in El Sereno while waiting for his family to pick him up after school. Hours later, a 33-year-old man was stabbed repeatedly on the same street, authorities said.
Surveillance video shows the moments just before the fatal stabbing of Xavier Chavarin, when the assailant walked up behind the teen brandishing a long sword. Montes said the man in the video was his ex-boyfriend.
Zapata, 32, was arrested Wednesday on suspicion of murder in Xavier’s death after barricading himself inside his Alhambra home for several hours during a standoff with Los Angeles police. Authorities say Zapata also stabbed the second man, who survived his wounds. Bail was set at $2 million.
Xavier’s murder has stunned his classmates at Woodrow Wilson High School, with counselors on hand to help the bereaved.
“I have a senior class and most of them were affected,” said Alan Chau, a social studies teacher who has known Xavier for three years. “We sat there all Monday and had discussions about it.”
The boy was a model student, Chau said, who taught him US history and was also his primary teacher.
“In general, Xavier is a calm boy, very open. He just went with the flow, ”said his teacher. “He is loyal to his friends at school. …he asked questions. He does not answer. He is a hard-working kid in the classroom.”
Xavier loved to draw, and Chau said he had expressed a desire to become a graphic designer, adding that the high school senior had set his sights on Los Angeles Trade-Technical College.
“The fact that they just took it from me breaks my heart,” said Laura Frías, Xavier’s mother, in a interview with NBC4.
The family went to the funeral home Wednesday to make final burial arrangements for their son.

Authorities surround an Alhambra residence where they believe a suspect who fatally stabbed a 17-year-old boy and injured a man in Los Angeles was barricaded.
(Irfan Khan/Los Angeles Times)
Hours before that, Los Angeles police detectives arrived at a home in the 2300 block of Westmont Drive in Alhambra after receiving a tip that the man living there was the same person seen on video of the shooter. with a knife, the commander. German Hurtado said. Officers from the LAPD’s Gang and Narcotics Division surrounded the home around 7 a.m., and a Special Weapons and Tactics team brought in two armored vehicles and sealed off the surrounding area.
Hurtado said a crisis negotiator was able to persuade Zapata, who was home alone, that it would be safe to leave. The crisis negotiator and a mental health assessment team, along with the man’s mother, spoke to him on a cell phone for hours before he turned himself in, Hurtado said.
The family of the police boy said the slain Zapata waited anxiously outside during the confrontation. Frías, her mother, broke down when Zapata’s surrender was announced. Her father, Jesús Frías, comforted her as she hid her face and wept openly.
Daniel Chavarín, the teenager’s father, wanted the police to take away the person accused of killing his son.
“It didn’t bring me any kind of relief, but it was…it was making sure he got caught,” Chavarin said.

Daniel Chavarin, left, father of 17-year-old Xavier Chavarin, who was fatally stabbed last week in El Sereno, speaks with police officers at the scene where the stabbing suspect barricaded himself in Alhambra.
(Irfan Khan/Los Angeles Times)
Although the motive for Xavier’s murder remains unclear, Councilman Kevin de León, whose district includes the site of the attack, said Wednesday that the streets of Los Angeles “are the largest psychiatric ward in the United States.”
“Unfortunately, it’s been pretty normal in Los Angeles for someone to go up to someone and break them … or just hit someone,” said De León, who was waiting outside Zapata’s house with Xavier’s family.
“No doubt about it; she has suffered from serious mental illness,” he said of the suspect in the stabbing.
Jorja Leap, a professor in the Department of Social Welfare at UCLA’s Luskin School of Public Affairs, disputed De León’s comments, saying it was “inaccurate and irresponsible” to paint Los Angeles with such a broad brush as depicting mental illness.
The Los Angeles Police Department and other law enforcement agencies do not track crimes committed by people with mental illness, Leap said.
“Many (people with mental health issues) can’t even care for themselves, let alone think about taking the life of another human being,” he said.
It was not immediately clear if Zapata had ever been diagnosed with mental health problems, but Montes and others said he was clearly not feeling well.
A woman who works at Valley Food Liquor on the block where the second stabbing occurred recalled a strange customer buying beer and cigars but not speaking, even when greeting him and trying to start a conversation.
The morose description matched the way Montes said Zapata had behaved in recent years.
The man she dated was friendly, comfortable and talkative, she said, but lately he had become withdrawn.
It wouldn’t look like it was there. He would shut up,” Montes said.
The two dated from 2008 to 2012, but Montes said he broke up with Zapata because of his methamphetamine addiction, which he said kept him up all night. They had been in a band called Narfarus, and Zapata was an extremely talented drummer who was touring with other groups, Montes said.
Court records show Zapata had minor run-ins with the law before this week.
He was convicted in 2013 of driving without a license and received a year of probation. In 2017, he was charged with driving with a revoked license, but prosecutors dropped the case. In September 2020, he was convicted of misdemeanor hit and run and driving with a blood alcohol level above the state limit. He spent two days in jail and was placed on probation for three years.
Montes has custody of her and Zapata’s teenage son. She said she hadn’t been in contact with Zapata for a while, but in the last two weeks he began texting and calling his son. He seemed paranoid, Montes said.
Still, he said, he had never seen Zapata be violent. “I never saw a side like that of him.”