UVALDE, Texas — Editor's note: This timeline has been updated throughout.
There is now an investigation into how police responded to Tuesday's mass shooting at Robb Elementary in Uvalde.
Investigators said one of the big questions is whether officers on site could have made attempts to enter the school to end the attack faster.
On Thursday and Friday, Texas Department of Public Safety briefings revealed details about the timeline of the shooting.
"This incident happened on Tuesday, May 24. So it was a lot of information, a lot of moving parts," Texas DPS Regional Director Victor Escalon said.
May 24 is a day the people of Uvalde will never forget. It's the day an 18-year-old shooter took the lives of 19 children and 2 two teachers at Robb Elementary.
Here is a timeline of events in the deadly shooting:
11 a.m.
According to officials, on Tuesday at 11 a.m., the killer sent messages on social media about his plans before shooting his grandmother.
11:28 a.m.
The 18-year-old shooter drove about two miles to Robb Elementary in his grandmother's truck. He crashed the vehicle outside the school and then jumped out of the vehicle with a bag full of ammunition and a rifle.
"He walks around, he sees two witnesses at the funeral home across the street from where he went. He engages them, fires towards them," Escalon said.
11:30 a.m.
Police receive the first 911 call about the crash and shots fired.
11:31 a.m.
A Uvalde CISD school resource officer was off-campus nearby when he heard gunshots outside the school. He drove over to the school and actually drove past the shooter as the shooter was going into the school.
11:32 a.m.
The gunman hops a fence at the school and starts shooting at the building.
11:33 a.m.
The shooter enters the classroom while shooting. He walked through an unlocked door that had been propped open by a teacher.
DPS acknowledged that information conflicted with what they'd said earlier in the week.
"It was reported that a school district police officer confronted the suspect that was making entry. Not accurate. He walked in unobstructed initially," Escalon said.
11:44 a.m.
"Local police department, Uvalde police department, the independent school district police department are inside making entry. They hear gunfire. They take rounds. They move back, get cover," Escalon said of the moments when officers first entered the school.
11:51 a.m.
Initially, three Uvalde Police Department officers gathered outside the classroom, which was locked by that point.
12:03 p.m.
As many as 19 officers including Uvalde PD, Zavala County deputies and others, were gathered outside the classroom. DPS said the officers believed the situation at that point had transitioned from an active shooter to barricaded subject. The incident commander on scene determined they needed more equipment to breach the barricade, so they waited.
The commander has been identified as the head of the school district police force.
12:10 p.m.
A teacher calls 911 to report that multiple children were killed.
12:15 p.m.
The Border Patrol special tactical team arrived.
12:17 p.m.
Uvalde CISD announced the shooting on Twitter.
12:18 p.m.
A teacher reports to 911 that nine students were still alive.
12:21 p.m.
Three shots were heard in the 911 call.
12:36 p.m.
A student called 911 and was told to stay on the line and stay quiet. A fellow student is heard on the call telling the caller to hang up.
12:43 p.m.
A student called the police and said to please send officers now.
12:50 p.m.
The Border Patrol team breached the doorway and shot and killed the suspect.
More about the Uvalde school shooting:
- Uvalde school mass shooting: What we know about the victims
- How to help the Uvalde community affected by the school shooting
- 'I was hiding hard' | Fourth grader who survived Uvalde school shooting gives heartbreaking account of gunman's classroom assault
- Daughter and her best friends 'are all gone now,' dad says
- Police: Texas gunman walked through apparently unlocked door, was inside school for 1 hour
- Husband of Uvalde teacher killed in school shooting has died from heart attack, their family says