New Canaan Police Department

A man in Connecticut has been arrested after allegedly killing his mom in a town many celebrities have called home ... and, his mug shot's quite startling.

Sebastian Van Stockum -- a 20-year-old man -- was arrested Friday after officers were called to a home in New Canaan, CT by someone who allegedly told them he'd killed his mom.

Emergency crews tried to perform life-saving measures on the victim -- who the police aren't public identifying yet ... but, the person was ultimately pronounced dead at the scene. Stockum has been charged with murder, and he's being held on $2 million bond.

Stockum's mug shot shows numerous cuts and abraisions on his face ... with hie eyes downcast away from the camera as he poses. Getty

New Canaan is a small, wealthy town a

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