Originally Published: 10 JUL 22 21:10 ET

Updated: 11 JUL 22 12:30 ET

By Rosa Flores and Rosalina Nieves, CNN

(CNN) -- The chairman of the Texas House committee investigating the Uvalde school shooting pushed to release hallway surveillance video that shows what police were doing as a gunman remained inside adjoining classrooms for about 77 minutes.

Rep. Dustin Burrows, the committee chairman, said Monday that releasing the hallway footage would be important because the public would see the evidence for themselves.

"I can tell people all day long what it is I saw, the committee can tell people all day long what we saw, but it's very different to see it for yourself, and we think that's very important," he said. "We'll continue to put pressure on the situation and consider all options and making sure that video gets out for the public to view."

However, Burrows is prohibited from releasing the 77-minute hallway video of the law enforcement response because he signed a non-disclosure agreement with Texas Department of Public Safety, he said on Twitter on Friday.

Burrows attached two letters to his tweet. In one letter, he asked the DPS for permission to release the video to the public. The other letter is a response from DPS saying that the agency agrees that the video will bring "clarity to the public regarding the tragic events in Uvalde," but that the Uvalde district attorney "has objected to releasing the video."

His tweet states that the video he is pushing to release "contains no imagery of victims or footage of violence."

Burrows also said the committee is looking to release a preliminary report on the shooting "sooner than later." The report could be released within the next 10 days, a source close to the committee had previously said.

The video would offer primary evidence of what responding police were doing when a gunman opened fire inside adjoining elementary school classrooms on May 24, fatally shooting 19 young students and two teachers. A mass of officers waited in a nearby hallway for over an hour before they breached the door and killed the gunman.

What officers were doing in those 77 minutes remains largely unclear, and some officials have questioned the trustworthiness of the various investigations working to understand what went wrong that day.

Last month, DPS Director Col. Steven McCraw criticized that delay as an "abject failure," in part citing evidence from the hallway surveillance video. Some images from the video were obtained by the Texas Tribune and Austin American-Statesman and showed that officers had significant firepower -- including rifles and a tactical shield -- well before they ultimately breached the door.

DPS director testifies for second time

The House committee began its latest hearing on Monday morning. The witnesses scheduled to testify were McCraw, ALERRT Assistant Director John Curnutt and Uvalde County Sheriff Ruben Nolasco.

On Thursday, Uvalde Mayor Don McLaughlin refuted a new assessment of the law enforcement response to the shooting, saying that the report by the Advanced Law Enforcement Rapid Response Training (ALERRT) Center "does not give a complete and accurate account of what happened."

McLaughlin took issue with the first part of the report, which said a Uvalde police officer with a rifle spotted the gunman outside the school, but a supervisor either did not hear the officer or responded too late when the officer asked for permission to fire.

"No Uvalde police department officer saw the shooter on May 24 prior to him entering the school," McLaughlin said in a statement. "No Uvalde police officers had any opportunity to take a shot at the gunman."

CNN reached out to Uvalde District Attorney Christina Mitchell Busbee on Friday and on Sunday asking her to comment on why she objects to the release of the video, but has not heard back.

According to the same source, the Texas House Investigative Committee's preliminary report will clarify conflicting accounts from previous reviews of what happened on May 24. The report will include verbatim quotes from sworn testimony, the source said.

Nolasco told CNN on Sunday his testimony will be through video-conference, not in person.

Texas House Speaker Dade Phelan (R) created the three-member committee last month. Burrows, a Republican, was appointed chairman; Rep. Joe Moody (D) was appointed vice chair; and former Texas Supreme Court Justice Eva Guzman is a member.

The purpose of the investigative committee is a fact-finding one. Two other House committees, Youth Health & Safety and Homeland Security & Public Safety, will be tasked with making legislative recommendations.