The gunman had purchased a total of 1,657 rounds of ammunition, 315 of which were inside the school, Steven McCraw, director of Texas Department of Public Safety, said Friday.

McCraw said 142 of those rounds were spent cartridges and 173 were live rounds.

Officials found 922 rounds outside of the school, but on school property. Of those rounds, 22 were spent cartridges and 900 were live rounds. Another 422 live rounds were found at the crash site, McCraw said.

The suspect had a total of 60 30-round magazines, 58 of which were at the school. He had fired nearly 200 rounds, most of them inside the school, said McCraw.

Five of the 17 people injured in the elementary school shooting remain in the hospital on Friday, according to officials.

Two children and one adult are being treated at University Hospital in San Antonio, two of whom are in serious condition, and two adults are at Brooke Army Medical Center, both in fair condition.

A 10-year-old girl was discharged from University Health in San Antonio.

Eight children and three adults were treated and discharged from Udalve Medical Center earlier this week.

-ABC News' Jennifer Watts

As part of its ongoing investigation into Tuesday's shooting, the Texas Department of Public Safety is conducting a review of law enforcement actions.

This comes after the visibly shaken Steven McCraw, the director of the Texas Department of Public Safety, revealed a cascading series of police failures before and during one of the deadliest school shootings in the nation’s history.

The incident commander, the chief of Uvalde ISD Police, wrongly believed the incident had transitioned from an active shooter situation to a barricaded subject situation, where the suspect had stopped firing and barricaded himself in a classroom, no longer posing a threat to children, McCraw said.

“He thought there was time,” McCraw said.

McCraw said there may have been a belief by the incident commander that no one was alive anymore inside the classrooms. But, he detailed multiple 911 calls made from inside the classrooms, on which callers explicitly said several children were alive and trapped inside with the shooter. Callers at several points asked for police to be sent in.

-ABC News' Aaron Katersky

Those inside a classroom with the shooter made several calls to 911, but the tactical unit that arrived at 12:15 p.m. waited 35 minutes before breaching the classroom, Steven McCraw, director of Texas Department of Public Safety, said at a press conference Friday.

A 911 call was made at 12:03 p.m. from room 112 and lasted 23 seconds. McCraw did not identify the caller.

She called back at 12:10 p.m. and advised that there were multiple dead in the classroom, McCraw said.

The person then called again at 12:13 p.m. and again at 12:16 p.m., when said there were eight to nine students who were still alive, McCraw said.

A call was made by someone else from room 111 at 12:19 p.m., the caller hung up when another student told her to hang up, McCraw said.

At 12:21 p.m., three shots were heard over a 911 call. At 12:36 p.m., another 911 call was made by the initial caller and it lasted for 21 seconds. The student caller was told to stay on the line and be very quiet. She told 911 that the gunman shot the door, McCraw said.

At approximately 12:43 p.m. and 12:47 p.m., she asked 911 to please send the police now, McCraw said.

The caller said she could hear police next door at 12:46 p.m. At 12:50 p.m., the Border Patrol tactical unit finally breached the door and shot the suspect.

Texas state Sen. Roland Gutierrez is counting down the days until the start of the next school year, which he said is 77 days.

Without change, "every day is one day closer to students dying," Gutierrez, a Democrat, told ABC News.

He is among the lawmakers calling on Texas Gov. Greg Abbott to convene a special session to address gun violence.

The senator also mentioned potential plans to tear down Robb Elementary and build a new campus.

"I want what families want. Every person has told me they don’t want to go back. Little kids I’ve met have told me they don’t want to go in that school," he said.

-ABC News' Marcus Moore and Darrell Calhoun