A new federal lawsuit claims a city police officer acting as a security guard didn't do his job and more than two dozen of his colleagues failed in their duties or violated the civil rights of surviving victims after the 2016 Orlando, FL, nightclub massacre, reports ABC News.

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The gunman, Omar Mateen, was fatally shot by police after 49 people were killed and 58 were wounded at Pulse nightclub in what was then the deadliest mass shooting in modern U.S. history.

Orlando police officer Adam Gruler, according to court papers filed Thursday in U.S. District Court, "was at Pulse at all pertinent times and was charged with providing security to Pulse. Instead, he abandoned his post."

The lawsuit also lists 30 unidentified Orlando police officers who the plaintiffs allege either remained outside the nightclub while the shooting occurred or held witnesses against their will after they fled the massacre. The city of Orlando is listed as an additional defendant.

In a joint statement, the city of Orlando and the Orlando Police Department said they have not seen the lawsuit, but that "federal, state and local law enforcement officers and first responders put themselves in harm’s way to save as many lives as possible."