ORLANDO, Fla. (Reuters) - Police gunfire was responsible for none of the civilian casualties at the Pulse nightclub in Florida as officers sought to end a rampage by a man who killed 49 people in the one of the deadliest mass shootings in U.S. history, state authorities said on Wednesday.

FILE PHOTO: An aerial view shows the Pulse gay night club after a mass shooting in Orlando, Florida, U.S. June 12, 2016. REUTERS/Carlo Allegri

In a report following a six-month investigation into the emergency response to the June 2016 massacre at the Orlando club, investigators determined that 14 responding officers had fired more than 180 shots during five attempts to take down the shooter, Orange-Osceola State Attorney Aramis Ayala said.

“All officers have been cleared of any wrongdoing,” Ayala said at the news conference on Wednesday. “No casualties were the result of friendly fire.”

The 29-year-old gunman, Omar Mateen, opened fire shortly after 2 a.m. local time during the LGBT-friendly club’s popular Latin night, shooting patrons on the dance floor and spraying bullets at others hiding in bathroom stalls.

He then took hostages during a three-hour-long standoff with police, claiming allegiance to a leader of the Islamic State militant group before he was shot dead by police.

During the briefing, Chief Assistant State Attorney Deborah Barra offered a minute-by-minute breakdown of the police response, using a diagram of the nightclub to explain the findings.

During the attack, the shooter’s assault rifle jammed after firing 186 shots, so he switched to his 9mm handgun and went toward the club’s bathrooms. There he called 911 five times and searched the internet before shooting other patrons hiding in the stalls, Barra said.

The final exchange between officers and Mateen was through a small hole officers blasted into the hallway in the bathroom area. Through that hole Mateen shot an officer in the helmet with the 9mm. Officers returned gunfire and struck Mateen multiple times including in the head, ending the confrontation.

Piecing together evidence from surveillance footage, 911 calls and witness testimony, investigators determined that majority of shots fired by police had struck the nightclub’s walls, tables, doors and other structural features of the club. A total of 400 shots were fired that night by police and Mateen.

“There is absolutely no evidence that anyone injured was fired by law enforcement,” Barra told reporters Wednesday.

“Each and every engagement - no civilian was struck. And each time the law enforcement officer pulled the trigger, it was reasonable and justifiable,” she said.

Ayala also issued clearance letters for all the officers involved in the incident.

At the time, the Orlando massacre was the deadliest mass shooting in modern U.S. history. It has since been surpassed by a 2017 attack in Las Vegas in which a sniper killed 58 concert attendees from the window of his hotel room.

The briefing also comes a day before the one-year anniversary of the massacre at Marjory Stoneman Douglas High School in Parkland, Florida, where 17 students and staff members were killed by a former student.