PHILADELPHIA (CBS) – Investigators say two teenagers are dead after a shooting took place at a party in Chester late Friday night.

The party was at Minaret Temple 174 located at 4th and Ward Streets.  Chester’s mayor, Wendell Butler, says it was a rental hall. He says information about the party went viral when it was posted on Facebook.

“From what I understand they started off with probably some sort of prank, a firecracker being tossed in the air which made people try to go to the exit. There must’ve been some words exchanged with whoever threw it and unfortunately that led into gunfire,” Mayor Butler said.

Police say nine people were reportedly taken to area hospitals after receiving gunshot wounds. Two of the victims were treated and released.

Mayor Butler confirmed to CBS 3 that two people have died since the shooting took place. The other five people remain at Crozer, with one in critical condition.

Friends and family confirm that one of the victims is 18-year-old Robel Laboy. Friends also confirmed that the second victim was a man named David Jones.

Oren Liebermann reports…

Mayor Butler says detectives are still piecing together what happened, “…because you have to understand, there probably was over 100 young people in the chaotic situation in trying to secure that location.”

Butler says the alleged 17-year-old gunman was arrested. “They have the shooter in custody. I think there were a couple of other arrests and one detective told me that they recovered four guns.”

And there was security at the party as well, “They had private security, now where they were from, I don’t know because they did not check in with my police department so we were unaware that anything was going on.”

Mayor Butler says kids as young as 13-years-old were said to be at this party. He says some came from as far as Philadelphia and Salem, New Jersey.

Reported By Hadas Kuznits, Mike Dougherty, KYW Newsradio; Jericka Duncan, CBS 3