A Texas Department of Public Safety (DPS) lieutenant told CNN on Thursday that officers were hesitant to enter Robb Elementary School on Tuesday because they “could’ve been shot.”

Speaking on “The Situation Room” with Wolf Blitzer, DPS Lt. Chris Olivarez said officers arrived at the school quickly but waited for reinforcements after they began getting fired upon by 18-year-old Salvador Ramos.

“Don’t current best practices, don’t they call for officers to disable a shooter as quickly as possible, regardless of how many officers are actually on site?” Blitzer asked.

“The active shooter situation, you want to stop the killing, you want to preserve life, but also one thing that – of course, the American people need to understand- that officers are making entry into this building. They do not know where the gunman is. They are hearing gunshots,” Olivarez said. (RELATED: ‘We Had No Idea This Was Goodbye’: TX Sheriff Attended Honor Roll Ceremony For Daughter Who Died Hours Later In Shooting)

“They are receiving gunshots. At that point, if they proceeded any further not knowing where the suspect was at, they could’ve been shot, they could’ve been killed, and that gunman would have had an opportunity to kill other people inside that school. So they we’re able to contain that gunman inside that classroom so that he was not able to go to any other portions of the school to commit any other killings.”

Olivarez said authorities are now trying to piece together an accurate timeline of events.

Ramos allegedly spent 12 minutes outside of the elementary school firing shots before he walked into the building and barricaded himself in a classroom, Regional Director for the Texas DPS, Victor Escalon, said Thursday, according to The Wall Street Journal (WSJ). Escalon could not provide any answers as to why no one stopped Ramos from entering the school.