police in maryland are hunting for a ` heartless ' thief who stole a four-year-old boy 's wheelchair in the middle of the night .
the youngster 's mother left the buggy in the lobby of their building on merrimac drive , langley park , as usual on sunday evening since it 's easier to carry her son to their second floor apartment .
but when she went to retrieve the stroller the following morning , it had reportedly disappeared .
george 's county police have released a piece of surveillance footage which shows a person pushing the empty chair in a parking lot .