A Bronx mother is pleading for help as she searches for her missing 20-year-old son with autism.

Claribel Castillo, the mother of Christopher Clarke, tells News 12 it is very unusual for her son to leave the house without warning. She says Christopher is on the autism spectrum, and although he's high-functioning, he doesn't have good social skills.

Surveillance video shows Christopher leaving their house on East 181st Street around 3 a.m. Monday.

Castillo says her son did not bring any money or ID with him, and he doesn't really know how to get around the area or use public transportation. She's been handing out flyers around the neighborhood, hoping someone would catch sight of him.

Christopher is 5 feet, 11 inches tall, and around 170 pounds and was wearing a black North Face jacket with black and white Adidas sneakers.

Castillo also says she believes someone may have taken his phone along the way and that she has no idea where he could be.

"I have no idea and that's what scares me,” she says. “At this point, I'm in fear if something happened to him along the way."

Christopher's mother says that he loves to play video games but doesn't really have any friends, and she's begging for anyone who may have seen him on the streets to please contact the police.