The shooter at a Texas elementary school on Tuesday was not confronted by officers and entered the building through an unlocked door, officials said Thursday.

The revelation corrects initial reports that school officers had attempted to stop the gunman from entering the elementary school before he barricaded himself in a classroom and killed 19 children and two teachers. The shooter entered the school around 11:40 a.m. on Tuesday and walked through the hallways until he eventually reached an open classroom, Texas police told reporters on Thursday.

PARENTS BEGGED POLICE FOR UPWARD OF 40 MINUTES TO STOP TEXAS SCHOOL SHOOTER: REPORT

"It was reported that a school district police officer confronted the suspect that was making entry — not accurate. He walked in unobstructed initially," said Victor Escalon, South Texas regional director for the Department of Public Safety. "So, from the grandmother's house to the car ditch to the school, into the school, he was not confronted by anybody, to clear the record on that. Four minutes later, law enforcement are coming in to solve this problem."

Police arrived on the scene by 11:45 a.m. but could not make immediate entry because the shooter had begun firing at the officers, Escalon added. It’s not clear whether the entire building was unlocked when the gunman entered the building, but Escalon said the doors may have been open.

"We will find out as much as we can why it was unlocked — or maybe it was locked. But right now, it appears it was unlocked," he said.

Texas police are attempting to piece together the timeline of law enforcement’s response to the mass shooting, which has prompted criticism from witnesses who said they had to plead with officers to enter the building for at least 40 minutes while the shooter was inside. Parents who were frustrated with the delayed response even tried to enter the elementary school, video evidence showed. Footage of the incident verified by the Washington Post on Thursday revealed new details about the timeline of the police response to the mass shooting that left 21 victims dead, including 19 children and two adults.

Officials said they will review the timeline by analyzing nearby traffic cameras and ballistics to determine who fired bullets and when.

The shooter, identified as Salvador Ramos, entered the building shortly after crashing his vehicle nearby, according to police. Before coming to the school, the 18-year-old shot his grandmother, who remains in the hospital, officials said.

CLICK HERE TO READ MORE FROM THE WASHINGTON EXAMINER

Uvalde is a town of roughly 16,000 people and is situated between San Antonio and Del Rio. The town is just dozens of miles away from the U.S.-Mexico border and has a Border Patrol station.

Police have not determined a motive for the attack. Several agencies are assisting with the investigation, including the Uvalde Police Department, the FBI, the Department of Homeland Security, and others.