The Uvalde school district’s embattled police chief has been fired following allegations that he made several critical mistakes during the mass shooting at Robb Elementary School that left 19 students and two teachers dead.

In a unanimous vote, the Uvalde Consolidated Independent School District’s (CISD) board of trustees dismissed police chief Pete Arredondo, three months to the day after one of the deadliest classroom shootings in US history.

“Coward!” parents yelled in a Uvalde auditorium as the meeting got underway.

Mr Arredondo is the first officer dismissed over the hesitant and fumbling law enforcement response to the May 24 tragedy.

Only one other officer — Uvalde Police Department lieutenant Mariano Pargas, who was the city’s acting police chief on the day of the massacre — is known to have been placed on leave for their actions during the shooting.

Mr Arredondo, who has been on leave from the district since June 22, has come under the most intense scrutiny of the nearly 400 officers who rushed to the school but waited more than an hour to confront the 18-year-old gunman in a fourth-grade classroom.

Most notably, Mr Arredondo was criticised for not ordering officers to act sooner. Colonel Steve McCraw, director of the Texas Department of Public Safety, has said Mr Arredondo was in charge of the law enforcement response to the attack.

Mr Arredondo was not in attendance with his career on the line.

Instead, minutes before the meeting of the Uvalde school board got underway, Mr Arredondo’s attorney released a scathing 4,500-word letter that amounted to the police chief’s fullest defence to date of his actions.

Over 17 defiant pages, Mr Arredondo is not the fumbling school police chief who a damning state investigation blamed for not taking command and wasted time by looking for keys to a likely unlocked door, but a brave officer whose level-headed decisions saved the lives of other students.

The letter also accused Uvalde school officials of putting his life at risk by not letting him carry a weapon to the school board meeting.

“Chief Arredondo is a leader and a courageous officer who with all of the other law enforcement officers who responded to the scene, should be celebrated for the lives saved, instead of vilified for those they couldn’t reach in time,” the letter stated.

Uvalde school officials have been under mounting pressure from victims’ families and members of the community, many of whom have called for Mr Arredondo’s termination.

Superintendent Hal Harrell had first moved to fire Mr Arredondo in July but postponed the decision at the request of the police chief’s attorney.

The Texas Department of Public Safety, which had more than 90 state troopers at the scene, has also launched an internal investigation into the response by state police.

Uvalde CISD did not immediately respond to a request for comment.