District Attorney Seth William's office engaged in "selective prosecution" based on race and class when he failed to charge the white building owner or the white architect overseeing the project, the NAACP's Philadelphia chapter said.
Williams is black. His office declined to comment Tuesday on the NAACP petition.
Six people were killed and 13 injured when a building being demolished collapsed on an adjacent Salvation Army thrift store in 2013.
A civil jury recently found the charity, building owner Richard Basciano and architect Platos Marinakos largely responsible for $227 million in damages.
The jury concluded the unlicensed contractor, Griffin Campbell, and a machine operator, Sean Benschop, were 1 percent responsible each. Yet Campbell and Benschop were the only ones prosecuted, the NAACP noted. Campbell is serving a 15- to 30-year term and Benschop half that time for six counts of involuntary manslaughter.
"If you have white and black all culpable in this and then the only ones sitting in jail are black, that seems to suit a lot of parties here, but it's unsettling for the NAACP," said Rodney Muhammad, the local chapter president.
Within days of the collapse, Benschop and Campbell were arrested, and their mugshots were "plastered" in the local media, he said. Meanwhile, Marinakos, the architect who got the demolition permits and hired the contractors, quickly cut an immunity deal with Williams' office.
Campbell, a long-time food cart operator, had bid $112,000 for the demolition work, about one-third of other bids. His trial lawyer, William Hobson, joined the NAACP on Tuesday and said he plans to use new evidence from the civil trial as he mounts an appeal.
"He was a pawn in the system. At most, he was not trained. He never should have been there," Hobson said of his client. "Prosecutors have a civic duty not to just seek convictions, but to seek justice."
Williams, amid an FBI probe of more than $65,000 in unreported gifts he received, is not seeking re-election this year.