Police said Mamo, 30, was sitting outside his booth shortly before 8 p.m. when several people approached him. A surveillance video captured a woman as she walked up and talked to Mamo for seven minutes. A second woman then approached with a man, then the two left. Moments later, police said, the man returned and hit Mamo in the side of the head with a brick.
The man and one of the women rummaged through Mamo's pockets and booth, then the three fled the area and got into an Old City cab, police said.
Several witnesses were in the area and are talking to police.
The man is described as a black man in his 30s with shoulder-length dreadlocks. He was wearing jeans and a black jacket at the time of the assault. One woman was wearing a pink sweat suit and carrying a yellow bag, the other had short hair and was wearing green pants and a dark jacket.
The reward money is only for information that will lead to the arrest of the male suspect. Police are also looking to speak with the two women.
Mamo was taken to Thomas Jefferson University Hospital, where his condition has since been upgraded to serious. He is from Ethiopia originally, according to his Facebook page.
E-Z Parks, the company that owns the lot, posted the reward through the Citizens' Crime Commission Thursday.
Anyone who has information is asked to call Central Detectives at 215-686-3093 or -3094. Efforts to claim the reward money may be made by calling 215-546-TIPS.
Contact staff writer Allison Steele at 215-854-2641 or email@example.com