DENVER (CBS4) – The family of an inmate who died after a scuffle with deputies at the Denver jail is demanding a federal investigation into his death following Thursday’s announcement by Denver’s district attorney that there will be no charges in the case.

“The deputies knew that he was mentally ill. Mr. Marshall had done nothing to threaten anyone, to take a swing at anyone, to attempt to escape, to do anything wrong,” said Darold Killmer, an attorney representing Marshall’s family.

Killmer made those comments in a news conference Thursday afternoon following the announcement by DA Mitch Morrissey that none of the deputies involved will face any charges.

“The force that we saw was not unreasonable in light of the situation the sheriffs were in,” Morrissey told CBS4’s Brian Maass in an interview.

Killmer was joined by Marshall’s niece Natalia and other members of Marshall’s family at the news conference. They say this is yet another failure by the justice system to hold law enforcment accountable.

Morrissey says multiple factors led to Marshall’s death and deputies did everything they could to help him.

Video from inside the Denver Jail that was released Thursday shows what happened the night Marshall died. Morrissey says it’s footage that supports his decision not to file criminal charges.

(credit: CBS)

An image from the video released Thursday showing Marshall in the Denver Jail (credit: Denver Sheriff)

“What struck me was the lack of aggressive behavior on part of these sheriffs,” Morrissey said.

Marshall’s erratic behavior toward another inmate on Nov. 11 is what is said to have caught the attention of deputies. That confrontation is shown on the video.

(credit: CBS)

(credit: CBS) (credit: Denver Sheriff)

Later, he is seen throwing things. He paces back and forth before finding a seat on a bench.

(credit: CBS)

(credit: CBS) (credit: Denver Sheriff)

When Marshall makes a move toward a deputy he’s taken to the ground, where he eventually vomits and stops breathing.

Morrissey thinks Marshall may have had a heart attack before deputies ever went hands on.

“I think there is a good argument to be made the heart attack may very well have started there,” he said.

In the news conference, Marshall’s niece called into question the size and number of officers used to restrain her 112 pound, 5-foot-4 uncle.

Natalia Marshall (credit: CBS)

Natalia Marshall (credit: CBS)

“That officer was three times his size,” Natalia Marshall said. “And on top of that that was five more that was involved.”

Morrissey says he knew the decision would come with opposition, but it won’t change.

“I am not going to charge people — anybody — for a crime that we don’t believe we can prove beyond a reasonable doubt,” Morrissey said.

The attorney for five of the six deputies who were involved says his clients are relieved with the DA’s decision not to prosecute.