A top Texas security official said Friday that police were wrong to delay storming the classroom where a teen gunman was holed up with dead and wounded children -- fueling fears that police inaction cost lives in Uvalde.

Police have come under intense criticism since Tuesday's tragedy over why it took well over an hour to neutralize the gunman -- who ultimately killed 19 children and two teachers at Robb Elementary School.

A teen gunman opened fire at Robb Elementary School in Uvalde, just over an hour west of San Antonio in Texas -- killing 14 children and a teacher
A teen gunman opened fire at Robb Elementary School in Uvalde, just over an hour west of San Antonio in Texas -- killing 14 children and a teacher GETTY IMAGES NORTH AMERICA via AFP / SCOTT OLSON

"From the benefit of hindsight... it was the wrong decision, period," Texas Department of Public Safety director Steven McCraw told an emotional news conference, at which his voice broke repeatedly as he was assailed by questions over the delay.

"From what we know, we believe there should have been an entry as soon as you can," McCraw said, adding: "If I thought it would help, I'd apologize."

An 18-year-old gunman killed 14 children and a teacher at the Robb Elementary School in Uvalde, Texas
An 18-year-old gunman killed 14 children and a teacher at the Robb Elementary School in Uvalde, Texas AFP / allison dinner

McCraw revealed in harrowing detail a series of emergency calls -- including by a child begging for police help -- that were made from the two adjoining classrooms where the gunman was barricaded.

But in seeking to explain the delay, he also said the on-scene commander believed at the time that the 18-year-old gunman Salvador Ramos was in there alone, with no survivors, after his initial assault.

Robb Elementary -- which teaches more than 500, mostly Hispanic and economically disadvantaged students from second through fourth grade -- called on parents not to pick up their children until all were accounted for
Robb Elementary -- which teaches more than 500, mostly Hispanic and economically disadvantaged students from second through fourth grade -- called on parents not to pick up their children until all were accounted for AFP / allison dinner

"I'm not defending anything, but you go back in the timeline, there was a barrage, hundreds of rounds were pumped in in four minutes, okay, into those two classrooms," McCraw said.

"Any firing afterwards was sporadic and it was at the door. So the belief is that there may not be anybody living anymore."

A girl cries outside the Willie de Leon Civic Center in Uvalde, Texas after a gunman killed 19 small kids and two teachers at an elementary school
A girl cries outside the Willie de Leon Civic Center in Uvalde, Texas after a gunman killed 19 small kids and two teachers at an elementary school AFP / allison dinner

McCraw separately told reporters, however, that a 911 call received at 12:16 pm -- one of several made from inside the classrooms -- reported eight or nine children still alive.

As many as 19 officers were outside the classroom door at that time, plus an unknown number of tactical team members who had just arrived, according to McCraw's timeline.

The door was eventually opened at 12:50 pm with keys provided by a janitor.

This undated screenshot from the Instagram account of Salvador Ramos, identified as the gunman in the May 24, 2022, shooting at Robb Elementary School in Uvalde, Texas
This undated screenshot from the Instagram account of Salvador Ramos, identified as the gunman in the May 24, 2022, shooting at Robb Elementary School in Uvalde, Texas social media via AFP

McCraw said the caller -- a child who dialed 911 multiple times -- begged for police to come. Her final call was cut off as she made it outside.

Texas Governor Gregg Abbott meanwhile told journalists who grilled him during a testy news conference Friday that he was given inaccurate information in the wake of the massacre.

Catholic faithful leave mass at Sacred Heart Catholic church in Uvalde, Texas, a day after a deadly school shooting devastated the town
Catholic faithful leave mass at Sacred Heart Catholic church in Uvalde, Texas, a day after a deadly school shooting devastated the town AFP / allison dinner

"I was misled," Abbott said. "The information that I was given turned out in part to be inaccurate, and I'm absolutely livid about that."

An undated screenshot from the Instagram account of Salvador Ramos, identified as the gunman in the May 24, 2022, shooting at Robb Elementary School in Uvalde, Texas
An undated screenshot from the Instagram account of Salvador Ramos, identified as the gunman in the May 24, 2022, shooting at Robb Elementary School in Uvalde, Texas social media via AFP

The powerful National Rifle Association kicked off a major convention in Houston Friday, but a string of high-profile no-shows underscored deep unease at the timing of the gun lobby event.

Former president Donald Trump criticized calls for tightened gun controls in remarks at the three-day annual convention, held around four hours' drive from Uvalde.

"The existence of evil in our world is not a reason to disarm law-abiding citizens," Trump said. "The existence of evil is one of the very best reasons to arm law-abiding citizens."

Thousands of gun enthusiasts descended on the event, filling a vast convention hall packed with booths displaying guns, walls of semi-automatic rifles and hunting products.

"This is it, this is the mega," said a man in his 60s, as he handled a new rifle he was considering purchasing.

But with millions of Americans grieving and angry following the Uvalde shooting, "American Pie" singer Don McLean led a wave of dropouts from the event, while Abbott said he would no longer appear in person.

McLean said it would be "disrespectful and hurtful" to perform at the "Grand Ole Night of Freedom" concert scheduled during the convention on Saturday. At least five other country music stars, including Lee Greenwood and Larry Gatlin, have also reportedly pulled out.

Facing mounting scrutiny, the gun manufacturer Daniel Defense -- which made the assault rifle purchased by Ramos -- also decided to stay away.

The Uvalde shooting was the deadliest since 20 children and six staff were killed at the Sandy Hook school in Newtown, Connecticut in 2012.

Highlighting the horror and trauma of the Uvalde massacre, 11-year-old Miah Cerrillo described smearing herself with the blood of a dead classmate in a bid to hide from the gunman, saying she lay there for what felt like hours until help finally came.

Cerrillo, whose hair has begun to fall out in clumps since the massacre, also told CNN that she and a friend scrabbled for their dead teacher's cellphone and used it to make an urgent plea to 911 operators for help.

Despite the scourge of mass shootings, efforts at nationwide gun control -- from banning assault rifles to mandating mental health and criminal background checks on buyers -- have repeatedly failed, although polls show support from a majority of Americans.