Ex-Pittsburgh Chief of Police Nate Harper did not appear at a news conference Friday because he was “embarrassed,” said his lawyer.

PITTSBURGH — Former city police Chief Nate Harper will plead guilty to charges that he conspired to steal city police funds deposited into unauthorized police credit union accounts and failed to file federal tax returns from 2008 to 2011, his attorneys said Friday.

Harper’s lawyers made the announcement at a news conference on a day of fast-moving developments in the federal investigation after prosecutors announced the grand jury indictment, Harper pleaded not guilty to the charges at an arraignment, and the judge said the former chief could remain free.

U.S. Attorney David Hickton called Harper’s actions “the worst kind of public corruption,” and said it was “a sad day” for authorities who had worked closely with the soft-spoken, generally well-liked and seemingly humble man on issues ranging from gang violence and security for the G-20 economic summit in 2009.

“This is puzzling and baffling behavior,” Hickton said.

Later, Harper begged off appearing at the news conference because he was “embarrassed and distraught,” defense attorney Robert DelGreco said. The 36-year police veteran has lost 20 pounds since Mayor Luke Ravenstahl demanded his resignation Feb. 20 after meeting with the FBI about the investigation, Harper’s attorneys said.

But the former chief, who came up through the ranks of Pittsburgh’s roughly 800-officer force and was chief since 2006, takes “full responsibility” for his actions, said Robert Leight, another Harper attorney.

“I think we’re prepared to plead to that indictment without modification,” DelGreco said.

The indictment alleges the 60-year-old Harper conspired with unnamed others to divert more than $70,000 from a city account into two unauthorized credit union accounts, then spent more than $32,000 of that himself. It includes a single charge of conspiracy and four counts of willfully failing to file income tax returns.

Although the federal crimes carry a maximum combined penalty of nine years in prison, Harper’s attorneys said guidelines dictate a likely sentence of 10 to 16 months — low enough for them to argue for probation or alternative incarceration, like house arrest.

Hickton said the investigation is continuing.

Ravenstahl denies any wrongdoing or being a target of the probe, though he acknowledged two bodyguards, also city officers, used debit cards from the same credit union accounts.