As the investigation into the mass shooting at a Texas elementary school continues, questions remain regarding the police response to the shooting. One of those questions has to do with the timeline of the shooting.

On Wednesday, Texas Department of Public Safety Director Steve McCraw said 40 minutes to an hour elapsed from when the shooter opened fire on a school security officer to when a U.S. Border Patrol team shot him to death. The next day, a department spokesman said authorities were still working to clarify the timeline of the attack.

“Right now we do not have an accurate or confident timeline to provide to say the gunman was in the school for this period,” Lt. Christopher Olivarez told CNN. He added it wasn’t clear if that 40-60 minute window began when the shooter got to the school or when he shot his grandmother at home before driving to the school.

According to a timeline given Thursday by department regional director Victor Escalon, the shooter was inside the building for at least 45 minutes before he was killed.

Once the shooter got to school, there had been unclear and contradictory accounts from police regarding whether he encountered a school resource officer. However on Thursday, Escalon said this was not the case, and that the shooter entered the school  “unobstructed” through a door that was apparently unlocked.

It also appears officers may have had issues once inside the school. The shooter had reportedly barricaded himself inside a classroom.

According to a law enforcement official who spoke to The Associated Press on the condition of anonymity, the Border Patrol agents had trouble breaching the classroom door and had to get a staff member to open the room with a key. Olivarez said investigators were trying to establish whether the classroom was, in fact, locked or barricaded in some way.

With the questions regarding the timeline of the Texas school shooting came criticism with another aspect of the police response. Witnesses on the scene reported frustrations with officers who had gathered outside the school.

“They say they rushed in. We didn’t see that,” Javier Cazares, the father of one of the victims. “They’re like, ‘Let us do our jobs.’ But their job is to us, go in and save lives, not wait.”

Upset that police were not moving in, Cazares 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.”