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.

Authorities shed more light on some of the suspect's digital footprint in the weeks and months before Tuesday's mass shooting.

In September 2021, suspected gunman Salvador Ramos asked his sister to buy him a gun and she "flatly refused," Steven McCraw, director of the Texas Department of Public Safety, told reporters during a briefing Friday. He did not note where this exchange took place.

On Feb. 28, in an Instagram group chat with four people, they discussed "Ramos being a school shooter," McCraw said.

The next day, on March 1, in an Instagram chat with four people, Ramos discussed buying a gun, according to McCraw.

Two days later, on March 3, in another four-person chat, someone said, "Word on the street is you are buying a gun," according to McCraw. Ramos reportedly replied, "Just bought something."

On March 14, Ramos posted on Instagram, "Ten more days," according to McCraw. Someone replied, "Are you going to shoot up a school or something?" to which Ramos replied, "No. Stop asking dumb questions. You'll see," according to McCraw.

Meta said it is working with law enforcement regarding the concerning messages sent on Instagram.

"The messages Gov. Abbott described were private one-to-one text messages that were discovered after the terrible tragedy occurred," Meta spokesperson Andy Stone said on Twitter. "We are closely cooperating with law enforcement in their ongoing investigation."

Investigators are also looking into people the suspect may have communicated with in video game chat rooms who "may have known something," McCraw said.

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