(NEW YORK) -- In the immediate aftermath of the Uvalde school shooting, Texas Gov. Greg Abbott praised the "amazing courage" of law enforcement, saying the incident that left 19 students and two teachers dead "could have been worse" if the officers hadn't run toward the gunfire and eliminated the shooter.
But as the investigation has unfolded since the May 24 massacre at Robb Elementary School, allegedly committed by an 18-year-old wielding an AR-15-style rifle and hundreds of rounds of ammunition, law enforcement and government officials have come under scrutiny for the twisting narrative about crucial elements of the police response.
In his press conference the day after the rampage, Abbott and officials from the Texas Department of Public Safety framed the response from police as being swift. But as more evidence has been uncovered, the timeline has been stretched from a rapid response to one that took 77 minutes from the time the shooter entered the school to when he was killed by officers.
"It's a mess," said Robert Boyce, retired chief of detectives for the New York Police Department and an ABC News contributor.
Boyce said that in a fluid investigation like the mass shooting in Uvalde, preliminary information is constantly changing.
"When I would do my press conferences, I would always say, 'This is what we have right now' and 'it's subject to change,'" Boyce said. "So, yes, it's not unusual for that to happen at all. Things change all the time, or you go back and look at the video and say, 'Alright, that didn't match up,' and people sometimes make assumptions that aren't true."
But Boyce said what has not changed is the basic tenet of the active shooter doctrine created after the 1999 mass shooting at Columbine High School in Colorado and shared by police departments across the country.
"The bedrock issue is to immediately go in and neutralize the threat," Boyce said. "People might say, 'Well, the cops weren’t wearing the proper vests.' My response to that is those kids had no vests on. So, I don’t want to hear that either."
Here are three major issues of the Uvalde shooting in which the official narrative from law enforcement and elected leaders has dramatically changed in the 10 days since one of the deadliest school shootings in U.S. history occurred:
Did a school police officer engage the shooter?
In his press conference the day after the shooting, Gov. Abbott said the alleged gunman, Salvador Ramos, shot his grandmother in the face, leaving her critically injured, before fleeing in her truck and crashing into a ditch outside Robb Elementary School.
"Officers with the Consolidated Independent School District ... approached the gunman and engaged with the gunman at that time," Abbott said.
But one day later, Victor Escalon, the South Texas regional director of the Texas Department of Public Safety, contradicted Abbott's statement.
Escalon said the school police officer wasn't at the scene when the suspect crashed outside the school. He said the gunman fired at two witnesses from a funeral home across the street.
"He continues walking towards the school," Escalon said of the suspect. "He climbs a fence. Now he's in the parking lot shooting at the school multiple times."
Citing security video outside and inside the school, Escalon said the suspect entered the school building unabated through a door on the west side of the campus.
He said numerous rounds were fired inside the school as officers were responding to the scene.
Escalon said the suspect walked 20 to 30 feet down a hallway, made a right and walked into a second hallway, made another right, walked roughly 20 more feet and turned left into a classroom that is adjoined to another classroom by a Jack-and-Jill restroom area. Police said that the children and teachers were killed in classrooms 111 and 112.
"Four minutes later, local police departments, Uvalde Police Department, the (Consolidated) Independent (School) Police Department are inside making entry," Escalon said. "They hear gunfire. They take rounds. They move back, get cover."
He said the officers tried to approach the locked classroom door where the shooter was, but the gunman fired at them through the door, hitting two officers. He said the officers called for additional resources, body armor, tactical teams and other equipment needed to take on the suspect.
Was the back door of the school left propped open?
On Friday, Col. Steven McCraw, director of the Texas Department of Public Safety, said the door the gunman used to access the school building was left propped open by a teacher prior to the shooter entering the school.
"The teacher runs to the room, 132, to retrieve a phone, and that same teacher walks back to the exit door and the door remains propped open," McCraw said during a press conference.
On Monday, Texas Department of Public Safety press secretary Ericka Miller confirmed to ABC News that investigators have now determined that the teacher closed the door, but that the door did not automatically lock as it was supposed to.
Don Flanary, a lawyer for the teacher, told the San Antonio Express-News that the teacher had propped the door open with a rock to carry food in from her car. He said that while the teacher was outside, she "saw the wreck" the suspect was involved in and "ran back inside to get her phone to report the crash.
As she went back out while on the phone with 911, the lawyer said, the men at the funeral home across the street from the school yelled, "He has a gun!" Flanary said.
"She saw him jump the fence and (that) he had a gun. So, she ran back inside," the lawyer said. "She kicked the rock away when she went back in. She remembers pulling the door closed while telling 911 that he was shooting. She thought the door would lock because that door is always supposed to be locked."
Law enforcement is looking into why the door did not lock, DPS confirmed to ABC News.
It took 77 minutes before the suspect was killed
The timeline on how quickly police responded to the shooting has changed several times, from a rapid response to about 40 minutes, to eventually 77 minutes before a SWAT team entered the classroom where the shooter was located and killed him, authorities said.
McCraw admitted on Friday that mistakes were made on the ground in response to the active shooter incident.
The missteps began before the shooting erupted at the school when a Uvalde Consolidated Independent School District police officer responding to a 911 call of a man with a gun on the school campus drove past the suspect, who was "hunkered down" behind a car in the school parking lot, McCraw said.
The gunman fired at the school multiple times before entering through the unlocked door. Police officials have given various times for when the shooter entered the school building, saying in one press conference that he gained access at 11:33 a.m., while in a different press conference they said 11:40 a.m.
McCraw said the shooter walked into a classroom and began firing more than 100 rounds.
McCraw said that by 12:03 p.m., there were as many as 19 officers in the school hallway. As the officers were outside the door, the incident commander -- Chief Pete Arredondo of Uvalde Consolidated Independent School District Police -- wrongly believed the incident had transitioned from an active shooting to a situation where the suspect had stopped firing, barricaded himself in a classroom and no longer posed a risk to children, McCraw said.
"He thought there was time to retrieve the keys and wait for a tactical team with the equipment to go ahead and breach the door and take on the subject at that point," McCraw said. "That was the decision, that was the thought process."
McCraw added, "Of course it wasn’t the right decision. It was the wrong decision."
Arredondo, who was sworn in this week as a Uvalde City Council member, has yet to offer a public statement on his response to the shooting.
But Escalon said last week that children trapped inside with the killer, who was freely walking back and forth between adjoining classrooms, made numerous 911 calls pleading for help.
Law enforcement officers from multiple agencies in the area converged on the school and began evacuating children from other classrooms and away from the two rooms where the gunman was holed up. Video and photos from the scene, showed children being pulled through broken windows and running out of harm's way.
Escalon said in one of the 911 calls from the classrooms where the mass murder was occurring, a dispatcher heard three shots in the background.
McCraw and Escalon cited numerous 911 calls coming in from students and teachers from 12:03 p.m. to 12:47 p.m., reporting that multiple students were dead, but others were alive. Escalon said at 12:47 p.m., a child called 911, begging, "Please, send police now."
It remains unclear whether information from the 911 calls was immediately passed on to Arredondo.
At 12:50 p.m., the SWAT team from Customs and Border Protection used a key they got from a janitor, entered the classroom and killed the gunman.
Meanwhile, video has surfaced showing frantic parents outside the school as the shooting was unfolding pleading with police to go into the school and being held back by officers, some who appeared to be armed with semi-automatic rifles and wearing bulletproof vests.
"I think the biggest issue that I see is that (classroom) door," Boyce said of the investigation into law enforcement's response to the shooting, which is being handled by the Department of Justice. "When did it get breached? When did they get that key?"
He said most patrol cars aren't equipped with forcible entry tools like rams, or anything to go through a locked door. But he said the officers should have asked for a sledgehammer or tools within reach to get through the door, or break windows to get into the classrooms.
"You take an oath as a police officer, there are days when you’re going to have to put yourself on the line," Boyce said. "You do what’s necessary to end the threat."
Citing the ongoing investigation, the Uvalde Consolidated Independent School District has not issued a statement on its police department's response.
Uvalde Police Chief Daniel Rodriguez issued a statement on his department's Facebook page last week, saying, "It is important for our community to know that our Officers responded within minutes alongside CISD officers. Responding UPD Officers sustained gunshot wounds from the suspect. Our entire department is thankful that the Officers did not sustain any life-threatening injuries."
Rodriguez added, "I understand questions are surfacing regarding the details of what occurred. I know answers will not come fast enough during this trying time. But rest assured, that with the completion of the full investigation, I will be able to answer all the questions that we can."