By Dave Savini

(CBS) — Chicago’s acting police superintendent says officers’ treatment of a detainee in their custody in December 2012 is under investigation, even though a much-criticized panel that looks into misconduct previously cleared the cops of wrongdoing.

Philip Coleman, 38, died at Roseland Community Hospital three years ago after he was taken into police custody and put in a cell. Newly released surveillance video obtained by CBS 2 shows officers crowding Coleman before one of them uses a Taser stun gun on him.

Video from another camera shows Coleman, apparently unconscious, being dragged along a corridor floor. Some officers appear to smile at the episode as they pass the camera.

It was no laughing matter, says Coleman’s family. They have filed a civil lawsuit against the city, alleging that the mentally unstable Coleman, a University of Chicago graduate, was mistreated while in police custody.

They called police when Coleman began acting erratically at home. Family members say he should have been transported to a hospital, not to the 5th District police station.

“This matter is under investigation, as it should be,” Acting Chicago Police Supt. John Escalante said in a prepared statement Monday. “While the independent investigation is ongoing we will be doing our own review of our policies and practices surrounding the response to mental health crises.”

A separate statement from Mayor Rahm Emanuel suggests allegations of misconduct will be reconsidered by the Independent Police Review Authority, which previously cleared the officers. IPRA has recently come under fire in another case, and the panel’s head was removed this week.

“I do not see how the manner in which Mr. Coleman was physically treated could possibly be acceptable,” Emanuel said. “Something is wrong here — either the actions of the officers who dragged Mr. Coleman, or the policies of the department. I have not received a sufficient answer on either from IPRA’s former leadership, and as a result I do not consider this case to be closed or the investigation into what happened that night to be over.”

Police reports say officers used the Taser on Coleman when he became combative.

The police station video — obtained by CBS 2 through the Freedom of Information Act — shows six officers entering Coleman’s cell as he lies sleeping. They wake him up. Coleman is seen standing up and soon falls down. An officer in the cell can be seen using the Taser. Another officer places Coleman in a headlock.

Video taken from another vantage point soon after shows a group of officers walking down a corridor as Coleman’s limp body is dragged on the floor. Some of the officers appear to smile.

Coleman was taken to Roseland Community Hospital. Police claim he was aggressive there, too, and they used the TASER on him again. The number of times is in question.

Coleman died at the hospital of an allergic reaction to a sedative, city officials have said.

The 2 Investigators obtained data showing the TASER was used on Coleman a total of seven times. Other records downloaded from the TASER guns show it was used on him 16 times.

Release of the video comes as the Chicago Police Department is under federal investigation for its practices, in the wake of the police-involved shooting death of a black teen in October 2014. Last week, Emanuel fired Supt. Garry McCarthy.

Settlement talks are underway between Coleman’s family and the city.

The complete statements from Escalante and Emanuel:

John Escalante — “This matter is under investigation, as it should be,” said Interim Police Superintendent John Escalante. “Independent of the facts that led to his arrest or the actions at the hospital, we are held to a higher standard and we must strive to live up to it every day. While the independent investigation is ongoing we will be doing our own review of our policies and practices surrounding the response to mental health crises.”

Mayor Rahm Emanuel — “I do not see how the manner in which Mr. Coleman was physically treated could possibly be acceptable. While the Medical Examiner ruled that Mr. Coleman died accidentally as a result of treatment he received in the hospital, it does not excuse the way he was treated when he was in custody,” said Mayor Rahm Emanuel. “Something is wrong here – either the actions of the officers who dragged Mr. Coleman, or the policies of the department. I have not received a sufficient answer on either from IPRA’s former leadership, and as a result I do not consider this case to be closed or the investigation into what happened that night to be over.”