(NewsNation) — Even as children called 911 and begged for help, the gunman at a Uvalde, Texas, elementary school was treated as a barricaded subject, and not an active shooter, the director of the Texas Department of Public Safety said Friday.

DPS Director Steven McCraw said the on-site commander during the shooting believed the gunman was barricaded in a classroom but that “there were no more children at risk.”

“A decision was made that this was a barricaded subject,” McCraw said. “There was time to retrieve the keys and wait for a tactical team with the equipment to go ahead and breach the door to take on the subject at that point.”

Nineteen officers were in Robb Elementary School for more than 40 minutes before the gunman was killed. Meanwhile, 911 calls were being made from inside classrooms by both teachers and students, pleading for police to help them.

“The belief was that there may not be anybody living anymore and that the subject is now trying to keep law enforcement at bay or entice them to come in,” McCraw said.

An on-scene commander thought more equipment and officers were needed to do a tactical breach, McCraw said. Border Patrol Tactical Unit, or BORTAC, was requested on scene. They were able to breach the door using keys they got from a janitor.

Despite acknowledging the “wrong decision” was made during the shooting response, McCraw declined to issue an apology for it during the press conference.

“If I thought it would help, I’d apologize,” he said in response to a reporter’s question.

Here’s what we know of the timeline:

11:27 a.m.: Video evidence shows the back door through which the gunman entered the school was propped open by a teacher. The gunman had crashed his vehicle in a ditch near the school and a teacher came out and checked on the driver, as did two people from a nearby funeral home, McCraw said.

11:28 a.m.: The gunman got out of the passenger side of the vehicle with a gun and the teacher ran back inside to get her phone and call 911.

11:30 a.m.: The teacher called 911 and reported the crash and that the driver had a gun.

11:31 a.m.: The gunman began shooting into school windows as he made his way toward the open back door.

11:33 a.m.: The gunman entered the school and began shooting in two classrooms. McCraw said the gunman had fired “at least 100 rounds” within the first four minutes of entering the school.

“We do know this: He shot more than 100 rounds based on the audio evidence at that time, at least 100 rounds,” McCraw said.

A school resource officer was not on site.

“The bottom line is that (school resource) officer was not on scene, not on campus, but had heard the 911 call with a man with a gun, drove immediately to the area, sped to what he thought was the man with a gun. (The officer went) to the back of the school, which turned out to be a teacher and not the suspect,” McCraw said.

11:35 a.m.: Three Uvalde police officers entered the school through the same door as the gunman, who fired at them. Two of the officers were struck by gunfire and suffered “grazing wounds,” McCraw said.

11:37 a.m.: The gunman fired about 16 more rounds while he was barricaded inside a classroom.

“There were 58 total magazines at the school,” McCraw said.

12:03 p.m.: As many as 17 more officers arrived and were inside the school, including the commanding officer. At the same time, an unidentified person called 911 from inside a classroom and whispered that they were in the room where the gunman was shooting. The call lasted for 1 minute and 23 seconds.

12:10 p.m.: The same person called 911 again and said there were multiple people dead.

12:15 p.m.: A tactical team entered the school building and joined the officers who were already there.

12:16 p.m.: One of the 911 callers reported that there were “eight or nine” people who were still alive.

12:21 p.m.: Three gunshots can be heard on 911 audio, followed by a child saying, “he shot the door.”

12:46 p.m.: A caller told 911 that they could hear police.

12:50 p.m.: Officers entered the classroom after getting keys from the janitor.

12:51 p.m.: A caller told the 911 operator that it sounded like officers were inside the room.

During the press conference, McCraw revealed more about the gunman’s digital footprint in the months before the shooting. On March 1, he said the gunman discussed buying a gun in a group chat over Instagram. On March 14, he made an Instagram post, saying, “10 more days,” according to the DPS director.

Someone replied to the post, asking the gunman, “are you gonna shoot up the school or something?”

“The subject replied, ‘No. And stop asking dumb questions and you’ll see,'” McCraw said.

In a Facebook message to another person, the gunman had said he was going to shoot his grandmother, McCraw said. He did so before he went inside the school on Tuesday. She was in serious condition as of Wednesday afternoon.

“Why and how is being looked at right now. And I’ll tell you this, hundreds of more, thousands of more leads are being looked at right now, because we haven’t answered all the questions. We haven’t gotten into the why,” McCraw said.

During Friday’s news conference, McCraw also said, “This is about finding facts and reporting facts as quick as we can. It’s not about trying to defend or it’s not about trying to assess or even be hypercritical of the facts.”

Read more here about how police response times in active shooter situations are vital to save lives and how things have changed since the Columbine High School shooting.