Law enforcement authorities in Texas are facing questions and criticism over how much time elapsed before they stormed an Uvalde elementary school classroom and put a stop to the rampage by a gunman who killed 19 children and two teachers

UVALDE, Texas -- Law enforcement authorities faced questions and criticism Thursday over how much time elapsed before they stormed an Uvalde elementary school classroom and put a stop to the rampage by a gunman who killed 19 children and two teachers.

Investigators were also unable to say with any certainty whether an armed school district security officer outside Robb Elementary exchanged fire with the attacker, 18-year-old Salvador Ramos, when he first arrived on Tuesday.

The motive for the rampage — the nation's deadliest school shooting since Newtown, Connecticut, a decade ago — remained under investigation, with authorities saying Ramos had no known criminal or mental health history.

During the siege, which ended when a Border Patrol team burst in and shot Ramo to death, frustrated onlookers urged police officers to charge into the school, according to witnesses.

“Go in there! Go in there!” women shouted at the officers soon after the attack began, said Juan Carranza, 24, who watched the scene from outside his house, across the street from the school.

Texas Department of Public Safety Director Steve McCraw said Wednesday that 40 minutes to an hour elapsed from when Ramos opened fire on the school security officer to when the tactical team shot him.

But a department spokesman said later that authorities could not give a solid estimate of how long the gunman was in the school.

“The bottom line is law enforcement was there,” McCraw said. “They did engage immediately. They did contain (Ramos) in the classroom.”

Meanwhile, a law enforcement official familiar with the investigation said the Border Patrol agents had trouble breaching the classroom door and had to get a staff member to open the room with a key. The official spoke on the condition of anonymity because he was not authorized to talk publicly about the investigation.

Javier Cazares, whose fourth grade daughter, Jacklyn Cazares, was killed in the attack, said he raced to the school when he heard about the shooting, arriving while police were still gathered outside.

Upset that police were not moving in, he raised the idea of charging into the school with several other bystanders.

“Let’s just rush in because the cops aren’t doing anything like they are supposed to,” he said. “More could have been done.”

“They were unprepared,” he added.

Carranza had watched as Ramos crashed his truck into a ditch outside the school, grabbed his AR-15-style semi-automatic rifle and shot at two people outside a funeral home, who ran away uninjured.Lt. Christopher Olivarez of the Department of Public Safety told CNN that the school security officer outside was armed and that initial reports said he and Ramos exchanged gunfire.