Originally Published: 27 OCT 22 06:42 ET

Updated: 27 OCT 22 10:51 ET

By Dakin Andone, Shimon Prokupecz and Matthew J. Friedman, CNN

(CNN) -- Texas Department of Public Safety Director Col. Steven McCraw is delivering Thursday the first formal, public update to his agency's oversight panel on its officers' actions during the May massacre at a Uvalde elementary school, after first facing victims' families who, furious over the response, are calling for his resignation.

"It's been five months and three days since my son, his classmates and his teachers were murdered," said Brett Cross, who was helping raise his 10-year-old nephew Uziyah Garcia before the boy was killed in the shooting.

But while the clock keeps ticking, Cross said, "Several numbers remain the same: It was 77 minutes that 91 of you all's officers waited outside while our children were slaughtered.

"We're not waiting any longer. Our families, our community, our state has waited long enough. And playing politics will only put the lives of more Texans at risk," Cross said, adding, "I expect ... your resignation immediately."

McCraw's remarks before the Texas Public Safety Commission will follow the referral of seven DPS officers for investigation by the agency's inspector general for what they did -- or didn't do -- as a gunman killed 19 fourth-graders and two teachers at Robb Elementary in the worst US school shooting in nearly a decade.

The session began with a public comment period, with five minutes per speaker, starting with state Sen. Roland Gutierrez, who represents Uvalde and said calls for McCraw's resignation are warranted.

Pointing not only to the errors of officers the day of the shooting, but the cascade of false information DPS put out in the weeks after, Gutierrez said the shooting "shattered" Texans' belief "we could trust the word and the actions of law enforcement -- especially the Department of Public Safety."

Both DPS and the commission had braced for relatives to speak, DPS sources said, adding the agency has reached out to coordinate this part of the meeting.

McCraw's comments are widely expected to be his most extensive and revealing yet about the DPS response. They'll come as the scourge of US school shootings shows no signs of abating, with at least 67 such attacks reported this year on US campuses, including a high school student and a teacher killed Monday in St. Louis.

While nearly 400 officers from DPS and 22 other agencies responded May 24 to the Uvalde campus starting within minutes of the first gunshots, law enforcement waited 77 minutes -- in violation of commonly held active shooter protocol and training -- before breaching adjoining classrooms to find the victims and kill the 18-year-old gunman.

Any disciplinary action DPS may be taking against any of its officers could be part of Thursday's report by McCraw, who has vowed to "tender (his) resignation to the governor" if his department is found to have any culpability.

Ahead of the meeting, Cross told CNN he planned to be there to address officials about "the accountability for their inactions."

Amid the investigation into how law enforcement responded to the carnage, though, the long-term impact on victims' families has been lost, Cross said.

"I don't believe that they feel or understand the aftereffects of this, but we're real people that lost the biggest things in our lives," he said. "And, these people that absolutely stood by and did nothing -- and still continue to do nothing -- get to go home and go to bed and sleep soundly through the night."

DPS scrutinized since initial narrative fell apart

Thursday's meeting will mark McCraw's first public testimony about the bloodshed in Uvalde since June, when before a state Senate committee he labeled the shooting response an "abject failure" -- but placed blame largely on local and school district police, including that agency's chief Pedro "Pete" Arredondo, who state authorities have said was the incident commander.

Arredondo, who has denied he was in that role, was fired in August -- a move his attorney called an "unconstitutional public lynching," adding Arredondo should be reinstated, with all back pay and benefits.

Arredondo was one of five school district officers at Robb Elementary, while DPS had 91 personnel respond to the shooting -- the most except for the US Border Patrol, according to a July report by a state House of Representatives investigative committee.

DPS increasingly has been scrutinized for its role in the response to the tragedy, beginning as its initial narrative of it unraveled within days of the bloodshed and expanding when body camera footage revealed to CNN that a DPS trooper arrived at Robb Elementary earlier than agency leaders would acknowledge publicly.

After an internal review of the actions of each DPS officer on the scene, seven were referred by the agency for investigation by the agency's inspector general.

Among them is state police Capt. Joel Betancourt, who tried to delay a team of officers from entering the classrooms, telling investigators he thought a more skilled team was on its way, CNN has reported.

Also included is Texas Ranger Christopher Ryan Kindell, who sources said told investigators he was focused on providing his bosses with updates and did not discuss options to breach the classrooms. He is seen in footage from surveillance cameras and body cameras speaking on the phone and, at one time, apparently offering to negotiate with the gunman.

McCraw has denounced similar attempts at negotiation by Arredondo, calling it the "wrong decision."

Another of the seven, Sgt. Juan Maldonado, was served termination papers, DPS said Friday, with sources confirming to CNN his firing was the result of his role in the response the day of the shooting.

Another officer, Crimson Elizondo, left DPS and took a job this summer with the school district police force. She, however, was fired after CNN revealed she was among those being investigated.

Each of these officers has either declined to comment or not responded when contacted by CNN.

The Public Safety Commission now includes four members -- all appointed by Gov. Greg Abbott. Many Uvalde victims' families, meantime, have been campaigning for Beto O'Rourke, Abbott's Democratic rival who has invoked the Uvalde response in arguing the governor's tenure should end.