"I heard three gun shots, I came to the window and I looked and I saw one guy lying on the ground," neighbor Renee Nu-Man who heard the shots, but was not at the scene, said.
One brother was taken to the Hospital of the University of Pennsylvania where he was pronounced dead.
The other suffered a graze wound to the head, but is in stable condition.
"There's at least, we believe, up to 30 people, 10 people playing basketball, and these kids are somewhere. They walk up to that crowd of spectators and they just begin firing," Lt. John Walker of the Philadelphia Police said.
"This is not a place we have problems. This is a rec center that is noted for its good programs and safety, quite frankly, in terms of being able to enjoy the facility," Commissioner Charles Ramsey said.
Police have made no arrests as of yet.
There is no motive at this time.
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