A second ex-New Orleans officer charged in an alleged conspiracy to cover up a deadly police shooting of unarmed residents after Hurricane Katrina is expected to plead guilty, a person familiar with the case said Tuesday.

A federal court filing Tuesday charges former detective Jeffrey Lehrmann with misprision of a felony, which meant he had knowledge of a crime and didn't report it. It said he "knew of a conspiracy among police officers to obstruct justice," helped conceal the conspiracy, helped create false reports and provided false information to federal investigators.

The shootings on the Danziger Bridge killed two people and wounded four others less than a week after the August 2005 storm's landfall and led to an investigation by the Justice Department.

Lehrmann left the New Orleans Police Department in 2006 and is a special agent at the U.S. Immigration and Customs Enforcement office in Phoenix. He was expected to enter a guilty plea this week, according to the person familiar with the case. The person was not authorized to discuss the plea negotiations and asked not to be identified.

Police are accused of fabricating witness statements, falsifying reports and planting a gun in an attempt to make it appear the shootings were justified. The cooperation of two key players in less than a month represents a major move forward by federal investigators as they seek enough evidence to charge a wider group of officers.

A bill of information only can be filed with the defendant's consent and typically signals a plea deal, but Lehrmann's attorney, Davidson Ehle, and U.S Attorney Jim Letten wouldn't comment Tuesday.

"Stay tuned," Letten said.

Ronald Madison, 40 and mentally disabled, and James Brissette, 19, were killed and four others shot as they crossed the bridge in search of food on Sept. 4, 2005.

"It's wonderful to see the justice system working the way it's supposed to," said Lorna Humphries, Madison's sister. "Maybe we can see the end of this and the community can begin healing."

The officers claimed they opened fire only after being shot at. Lance Madison, who accompanied his brother, Ronald, testified less than a month later that a group of teenagers started shooting at them before they encountered police.

"We have our defense," said attorney Frank DeSalvo, whose client, Sgt. Kenneth Bowen, was charged in state court. "We know what happened and it is not going to change no matter what other people say."

The second officer charged in the federal case, Michael Lohman, a retired lieutenant, pleaded guilty last month to conspiracy to obstruct justice.

An ICE spokesman in Phoenix said he couldn't immediately comment on the case. A voice mail left at Lehrmann's office was not immediately returned. Lehrmann is due in court Thursday.