Updated

A former police lieutenant pleaded guilty Wednesday to conspiring to obstruct justice after federal officials say he helped cover for officers who killed two people on a bridge in the chaos following Hurricane Katrina.

Federal investigators say former Lt. Michael Lohman knew two people shot to death as they crossed the Danziger Bridge had no weapons, but he and others filed false reports to make the shootings seem justified. Four other people were wounded.

Family members of the victims gathered at the downtown federal courthouse as Lohman arrived to enter his plea.

"We are very, very happy about the progress that the FBI and the U.S. Justice Department have made," said Dr. Romell Madison, brother of Ronald Madison, who was killed on the bridge. "It's a tremendous relief for us to see some sort of closure. The people of New Orleans should be relieved that there is still justice for everybody here."

Seven officers were charged with murder or attempted murder in the Sept. 4, 2005, shootings, just days after Katrina smashed levees and flooded 80 percent of the city. But a state judge dismissed the charges in 2008.

Until Lohman's plea Wednesday no one had been prosecuted in the deaths of Madison, a 40-year-old mentally disabled man, and 19-year-old James Brissette. Four others were wounded.

Survivors have said the officers fired at unarmed people who were crossing to get food at a grocery store. The officers acknowledged shooting at people on the bridge, but claimed they did so only after being fired on.

The Danziger case is one of the best-known incidents of violence involving police after Katrina, a time in which confusion across the flooded city led to widespread reports, many later discounted, of police and rescuers being fired on.

Lohman, now 42, supervised the initial probe of the officers' actions at the bridge, which spans the Industrial Canal and connects the working-class Gentilly neighborhood with eastern New Orleans. Both areas were extensively damaged in the storm.

His investigation drew U.S. Justice Department attention after the state judge dismissed charges against the seven officers.

Federal officials say Lohman knew another investigator planned to plant a gun to justify the shooting and asked if it was "clean," meaning it could not be traced back to another crime, according to the documents. The investigator assured him it was and he went along with the plan to plant it.

After Lohman's plea, U.S. Attorney Jim Letten said the investigation continues. He called the case "a pretty elaborate ongoing conspiracy." He declined to say whether higher-ranking police officials might have been involved.

"We are going to follow the evidence wherever it takes us," he said.

Lohman went to the scene of the shootings, saw that the victims had no weapons, and concluded the shooting was unjustified, according to the bill of information. Then he and other unnamed officers conspired to cover that up by filing false statements on a police report about the incident, according to the documents, which does not name the other officers.

The plan was "to ensure that the shootings would appear to be legally justified and that the involved officers would therefore be shielded from prosecution and liability," the documents said.

A lawyer for one of the officers originally charged in the shootings said federal investigators have been looking into what they described as a "corrupt investigation."

So far, lawyers for two other officers have identified their clients as targets of the probe.

The documents unsealed Wednesday allege Lohman and two unidentified sergeants drafted different versions of a false incident report on the bridge shootings in October 2005.

Among claims in the false report was a statement by one of the victims that she had seen her nephew and others firing guns on the bridge.

Federal officials say Lohman drafted his own 17-page false report after becoming dissatisfied that another investigator's false account was not logical.

"On several occasions in or about October 2005, defendant Lohman reviewed drafts of the false report written by the investigator and counseled the investigator on ways to make the story in the report sound more plausible," according to court documents.

The documents said Lohman also told the investigator to speak with each of the shooters to ensure they were "OK with" the false report, and were willing to give statements consistent with it.

"It's pretty incredible stuff, said Gary Bizal, lawyer for Jose Holmes, Jr., who said he was shot several times as he lay on the ground but survived. "It's like a script from Hollywood."

Lohman is to be sentenced May 26.