For weeks, an elderly woman complained to her family about strange knocking sounds coming from beneath her El Sereno home late at night. On Thursday, police made a terrifying discovery.

The noises were not of stray opossums or raccoons, but of a man, supposedly naked and, according to authorities, living in the crawlspace beneath the woman’s home.

The noises “normally occurred late at night, so we attributed it to there being animals in the house,” explained the woman’s son-in-law, Ricardo Silva. told NBC News.

But on Thursday, the sounds were much louder than usual, prompting the 93-year-old woman’s family to call police, she said.

The Los Angeles Police Department responded to a call in the 3600 block of Locke Avenue around 10:30 p.m. Thursday and discovered the man under the house, according to an LAPD spokesperson.

The man refused to come out of his underground home and officers called in a SWAT team to assist with the arrest, the spokesman said. A standoff ensued that lasted hours before the man was arrested on suspicion of trespassing, he said. Police remained at the scene until 5 a.m., he said.

“He refused to leave,” Silva told NBC News. “He wasn’t afraid of the (police) dogs and the first two attempts to use (tear gas) failed to get him out.”

Police identified the suspect as Isaac Betancourt, 27, according to NBC News, which reported that he was naked when he was found.

Betancourt was arrested by Los Angeles police at 4:25 a.m. Friday and charged with a misdemeanor, according to the Los Angeles County Sheriff’s Department. He was released Saturday afternoon and is scheduled to be arraigned Dec. 6.

Betancourt was previously arrested in July 2022, August and October 2023 and this year in March and August, according to the LASD Inmate Information Center.

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This story originally appeared on Los Angeles Times.