Police: 44-year-old man attacked, robbed in Dyker Heights

An assault was caught on camera of a 44-year-old man who was robbed in an unprovoked attack in Dyker Heights in Brooklyn, police say. 
The man was sitting on a stoop and talking on a cellphone when an unknown man went up to him and started beating him up.
The victim was punched and kicked, before his attacker took his cellphone and wallet. The wallet had approximately $6,000 in it.
The alleged suspect was seen wearing a black long-sleeved t-shirt with graphics on the front and back.
If anyone knows any information that can help, they are advised to call police.