Dallas ISD officials are holding a news conference Thursday at 11 a.m. to provide an update on the shooting at Wilmer-Hutchins High School on Tuesday.

Officials said earlier this week a student was allowed inside the Dallas school through an “unsecured door” with a gun and opened fire, wounding at least four of his peers and drawing renewed attention to the school district’s security measures.

The student, identified as Tracy Haynes, 17, turned himself in to police Tuesday night. He faces an aggravated assault mass shooting charge.

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It was the second shooting that Wilmer-Hutchins students have faced in a year. District officials denied protocol failures allowed the shooting to occur at a Tuesday news conference, a contrast from their response to last year’s incident.

Officials last year said the district’s security protocols were not strictly followed when a teenage suspect shot a classmate. Students said they did not feel safe at school and demanded that the district do more to protect them.

Multiple students said at the time that the school’s metal detectors were not regularly used and the school did not consistently enforce its clear bag policies.

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Dallas ISD board president Joe Carreón said on Wednesday that the district introduced increased security measures last year related to “the actual entry and intake of students, and ensuring that training on those procedures occurred not just in the beginning of the year, but also throughout the year, to stay fresh and conscious.”

District leaders said they would increase personnel during arrival and dismissal, retrain staff on backpack searches and metal detectors, and revamp schedules to make more people available to monitor students.

Dallas ISD Superintendent Stephanie Elizalde said at the time that the school had vulnerabilities, due to its many entrances, and Dallas ISD police Chief Albert Martinez would work with the school to identify them. She said the chief would lead an “after-action study and report” to understand what lessons could be learned.

“In this instance, yes, the metal detector went off, and there wasn’t a challenge. There weren’t the secondary steps that should have happened. And that’s our concern,” Martinez said.

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District officials did not immediately respond to a request for comment Wednesday on the steps taken last year to address the vulnerability Elizalde described, nor what steps the district would take to keep students safe when they return to campus next week.

Dallas ISD police Assistant Chief Christina Smith said Tuesday’s shooting was not the result of a “failure of our staff, of our protocols, or of the machinery that we have.”

Dallas schools’ emergency operations plans are revised annually, and Wilmer-Hutchins’ was up to date at the time of Tuesday’s shooting, Carreón said.

“What this board will do, and what this superintendent is committed to doing, is be fully transparent,” he said in an interview. “Without a doubt, the board will be briefed, the board will provide feedback, and the superintendent will bring forth recommendations on how we should avoid situations like this specific one moving forward.”

In the aftermath of an active shooting like Tuesday’s, investigators typically focus on how the weapon entered the school, how quickly law enforcement responded and how effectively school officials carried out emergency procedures, said J. Pete Blair, director of the Advanced Law Enforcement Rapid Response Training Center at Texas State University.

Last year, Martinez had also pointed to alternative methods for the school’s security to ensure safety, including campus security teams, door checks to make sure they are locked and audits performed by several agencies.

The number of entrances and exits on school campuses has long presented challenges for security, even before the rise in school shootings, Blair said. Efforts to route students through security-screened entrances — using metal detectors or other measures — are sometimes undermined by the need to keep other doors accessible for emergency evacuations, such as during a fire.

“This has been a common problem in schools,” Blair said in an interview.

Haynes entered the school on Tuesday after another student let him in through an “unsecured door,” an officer wrote in an arrest warrant affidavit obtained by The Dallas Morning News. The affidavit says the student who allegedly let Haynes inside was “unidentified” and describes school surveillance footage reviewed by police that captured the moments before and after the shooting.

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Haynes then displayed a firearm and opened fire “indiscriminately,” appearing to take a “point-blank” shot at one student, the affidavit says.

Jason Evans, a Dallas Fire-Rescue spokesperson, said three male students between the ages of 15 and 18 were “confirmed to have been injured by gunfire,” while a fourth male student, whose age was not known, suffered a “musculoskeletal injury” to the lower body.

A fifth person — a 14-year-old girl who was not shot — was also taken to a hospital with symptoms related to anxiety about an hour after the initial four students, he said.

Evans said Wednesday morning that two of the males had been discharged, while the other two remain hospitalized for “observation following procedures to address their injuries.”

Haynes was held Wednesday in lieu of a $600,000 bond, according to jail records. It was not immediately clear whether he had an attorney.

Elizalde, the superintendent, said during the news conference that classes were canceled at the high school for the rest of the week and mental health support would be available for those who need it. Classes will resume on April 22.