Survivors, including children, were calling the 911 emergency number from the classroom long after 18-year-old Salvador Ramos had entered with an AR-15 semi-automatic rifle, while police officers were in the hallway outside the room waiting for more assistance, according to Colonel Steven McCraw, director of the Texas Department of Public Safety.

In hindsight, McCraw told reporters at a news briefing, “it was the wrong decision” for the onsite commander to wait for a specially trained tactical team before trying to enter the classroom.

Someone whom McCraw did not identify called 911 multiple times starting at 12:03 p.m., telling police in a whisper that there were multiple dead and that there were still “eight to nine” students alive, the colonel said. A student called at 12:47 p.m. and asked the operator to send police “now.”

Officers did not go into the classroom until 12:50 p.m., according to McCraw, when a U.S. Border Patrol tactical team used keys from a janitor to open the locked door and kill Ramos.