The car's owner reportedly left the vehicle running on Union Street in Park Slope on Saturday evening when someone hopped inside and sped off.
Brandon Simeon, 54, who has autism, was still in the back seat. Simeon is approximately 5'6" tall and approximately 125 pounds. He was last seen wearing a green polo shirt and black pants.
The vehicle is a black 2010 M35 Mercedes with license plate 'FAL7278.'
Anyone with information is asked to call police.
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