A gun discharged inside a high school classroom. It took LAUSD 3 days to confirm reports

A loud bang heard Friday afternoon at Carson High School was from a gun that discharged inside a classroom with students present, according to Los Angeles school officials, who updated a previous release stating that no shot had been fired.

No injuries were reported. The district did not say where the gun was located when it discharged.

A student ran out of the classroom and off-campus immediately after a "loud bang," according to district sources who were not authorized to provide these details and requested anonymity.

The gunfire happened three days after a 10-year-old fourth grader brought a loaded semiautomatic pistol to Glassell Park Elementary School.

On Friday a district spokesman said in a statement that school police had "investigated a concern of a 'loud bang' on campus at Carson HS. Preliminary investigation shows no evidence that a shooting occurred."

But the investigation continued, and on Monday officials said they'd reached a different conclusion.

"Over the weekend, our School Police and Facilities departments continued to investigate this matter and a bullet fragment was found in the classroom, near where the loud noise was reported," Principal Sonia Buenrostro wrote in a communication to parents and staff.

She added: "In an abundance of caution, School Police will have an officer on campus for the remaining days of school. We will also provide mental health support to any student impacted by this incident."

In 2011, the accidental discharge of a gun inside a backpack in a class at Gardena High wounded two students, one critically.

Read more: 10-year-old brings loaded handgun to L.A. school amid rise in school crime, fights

Monday was the last day of school for students, but teachers had the option of returning to campus Tuesday for a paid work day to close out the school year.

A student bringing a gun to campus would typically be arrested — although not necessarily prosecuted. The district has, in the past, reported arrests without identifying students.

Officials on Monday refused to say what happened regarding a student suspected of bringing the gun to campus. School police are handling the investigation.

Senior district officials had recently identified 20 middle and high schools to receive extra counseling support as well as an officer stationed on campus from May 13 through the end of the school year amid rising school crime and fights.

That plan collapsed after one day amid pushback from anti-school police activists, including students, as well as from some school board members, who had not been alerted in advance.

This year, through April 15, there were 903 weapons incidents at LAUSD schools. Since then, incidents have included the May 3 arrests of two students carrying loaded semiautomatic handguns around Northridge Middle School. A Washington Preparatory High School student carrying a weapon shot and killed a student just off campus April 15.

In the Glassell Park Elementary incident, a 10-year-old boy brought a loaded .40-caliber Glock 22 to campus. The gun had been reported as stolen. A student who saw the boy show off the gun reported it to an adult, district sources told The Times. District officials neither confirmed nor denied those details.

Later this month the school board has scheduled a meeting to discuss school safety issues.

Times staff writer Andew J. Campa contributed to this story.

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This story originally appeared in Los Angeles Times.