Uvalde school district police Chief Pete Arredondo spoke out about the reason behind the 77 minutes delay in response when a gunman entered the Texas school to carry out a massacre that claimed 21 lives.

A hard-to-find key to a locked classroom door was the ultimate reason, the under-fire police chief said.

Arredondo was in charge during the May 24 mass shooting in Texas. In the interview with Texas Tribune, he defended law enforcement’s delayed response in taking down 18-year-old shooter Salvador Ramos.

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The Texas police have come under high scrutiny over its response to the shooting with many saying that if law enforcement acted on time could have reduced the number of casualties.

“Not a single responding officer ever hesitated, even for a moment, to put themselves at risk to save the children,” Arredondo told the newspaper. “We responded to the information that we had and had to adjust to whatever we faced.”

The door to the classroom that Ramos was in had a steel jamb and could not be kicked in, Arredondo said, adding that he spent more than an hour in the hallway trying dozens of keys to unlock the door.

“Each time I tried a key I was just praying,” Arredondo told the Texas Tribune. “The only thing that was important to me at this time was to save as many teachers and children as possible.”

In the first 40 minutes, Arredondo says he was waiting to receive the set of keys. He called for tactical gear and a sniper. Dozens of keys finally arrived, but none of them opened the door.

“My mind was to get there as fast as possible, eliminate any threats, and protect the students and staff,” Arredondo said.

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One hour and 17 minutes after Ramos started his rampage with an AR-15 style gun, police finally breached the door to the classroom and killed the gunman.

The Texas Department of Public Safety, which is investigating the shooting and the subsequent police response, does not support Arredondo’s account.

DPS said that while the incident should have been treated as an active shooter, Arredondo erroneously treated it as a barricaded suspect incident.