By Pat Loeb

PHILADELPHIA (CBS) — There is a guilty plea in the deadly 2013 Center City building collapse.

Sean Benschop has pleaded guilty to six counts of manslaughter and other charges. He also agreed to cooperate in the case against his co-defendant.

Benschop was the man who was operating the excavator on the morning of June 5th, 2013, when a brick wall being demolished fell onto the roof of a Salvation Army thrift store at 2140 Market Street in Philadelphia. The search for survivors continued until the next morning.

He was hired by a contractor to demolish the building and he did it in a “recklessly unsafe manner,” he admitted in court on Tuesday.

His attorney Bill Davis says he is deeply remorseful.

“He took responsibility for something that I think would be hard for anybody to look in the face and take responsibility for, but he did that.”

His sentencing is scheduled for October. The Philadelphia District Attorney’s office has agreed to seek no more than 10 to 20 years.

Prosecutor Jen Selber says, “While the effects were devastating with so much loss of life and injury, we also take into account the fact that it wasn’t intentional.”

Selber says Benschop has agreed to help the prosecution of the contractor who hired him, Griffin Campbell.

No one else has been charged in the case, which troubles Nancy Winkler, mother of one victim.

She says, “Others played a role and have yet to be held accountable.”

Killed in the collapse were Juanita Harmon, Roseline Conteh, Mary Simpson, Kimberly Finnegan, Ann Bryan, and Borbor Davis.

Blood tests showed Benschop had marijuana and prescription narcotics in his system on the day of the accident.