Enlarge By Cheryl Gerber, AP Dr. Romell Madison, left, Lance Madison and Jackie Madison Brown talk to attorney Mary Howell in New Orleans on Wednesday after Michael Lohman pleaded guilty to conspiring with fellow NOPD officers to obstruct justice by covering up a police-involved shooting that killed their brother, Ronald Madison, during the aftermath of Hurricane Katrina in 2005. NEW ORLEANS  A retired New Orleans police lieutenant pleaded guilty Wednesday to conspiring to cover up a deadly police-involved shooting in the aftermath of Hurricane Katrina in 2005. The plea in U.S. District Court by Michael Lohman, 42, is part of an investigation by federal agents into several police shootings of civilians in the chaotic days immediately following Katrina. Lohman faces up to five years in prison at his sentencing May 26. Seven officers were charged with murder or attempted murder in the Sept. 4, 2005, shootings, six days after Katrina made landfall and then battered the region. The charges were later dismissed. The incident happened when a group of police and other law enforcement officers in a large Budget rental truck confronted six people crossing the Danziger Bridge in eastern New Orleans, according to a police report. REPORT: No crime wave among Hurricane Katrina evacuees Police fired at several of the people, killing Ronald Madison, a 40-year-old mentally disabled man, and James Brissette, 19, the report said. The officers claimed they were fired at first, although surviving witnesses dispute that claim and say police opened fire on unarmed people. According to federal documents unsealed Wednesday, Lohman arrived after the shooting and encouraged the supervising officers to falsify their stories to "make it appear as if the civilians who were shot on the bridge had shot first at officers." He also approved the planting of a gun at the scene to justify the shootings, according to the documents. On Sunday, survivors of the Danziger Bridge incident, their families and lawyers applauded the guilty plea and said they hoped more will follow. "The fact that you have an officer who supervised these officers admitting he conspired to cover up — it doesn't get much better than that for vindication," said Gary Bizal, attorney for Jose Holmes, who was shot several times in the stomach during the shooting. Holmes was initially charged with shooting at officers but those charges were later dropped, Bizal said. The case is part of a wider probe that could bring more convictions, according to prosecutors. The FBI has confirmed its investigators are looking into at least three separate incidents where police shot eight people, killing four of them and badly injuring several others. Over the past 1½ years, federal investigators have summoned dozens of New Orleans police officers to testify before federal grand juries and seized police records. Jim Letten, U.S. Attorney for eastern Louisiana, said Lohman is expected to cooperate with investigators and federal agents will continue with all the investigations. "We will forge ahead," he said. "Our evidence is strong." Federal investigators also are looking into the shooting death of Henry Glover, whose remains were found inside an abandoned, incinerated car in Algiers, La., and Matthew McDonald, a drifter from Connecticut who was shot and killed by police in the Faubourg Marigny neighborhood of New Orleans five days after the storm, the FBI said. Copyright 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more