The gun used by a former student who opened fire Monday at a St. Louis high school was previously removed from his home at the request of his mother, authorities said.

On Oct. 15, more than a week before a teacher and a student were killed in the shooting at Central Visual and Performing Arts High School, St. Louis police received a call for a “domestic disturbance” at the suspect’s home, according to a Wednesday statement from the department.

The suspect’s mother found an AR-15-style rifle in the family’s home and contacted St. Louis police to have it removed, interim St. Louis police Commissioner Michael Sack said at a Wednesday news conference.

Police “determined at that time the suspect was lawfully permitted to possess the firearm,” according to the statement. The family worked with police to transfer the gun to a third party known to the family, Sack said.

The firearm that was removed was the same one used in Monday’s shooting that left two people dead and seven others injured, police confirmed in the statement.

“The mother wanted it out of the house, so they facilitated it,” Sack said. “…How he acquired it after that, we don’t know. We’re looking into it.”

While the suspected gunman’s family was “aware” he had obtained the gun, it was unclear when and how he got it, Sack said, adding that the federal Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating the gun sale. Police identified the suspect as Orlando Harris, 19.

Family cooperating with investigation, police official says

The suspect’s mother “has been fully cooperative” in the investigation into the shooting at Central Visual and Performing Arts High School and is “heartbroken for the families in this incident, for the school and the alumni,” Sack said Wednesday.

An investigator who interviewed the mother and her adult daughter Wednesday said the family was aware of the suspect’s mental health issues and “appears to have done everything they could have possibly done to try to help,” including monitoring his mail and getting him back into therapy and on medication, Sack said.

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Threats spike after shooting

St. Louis area schools have seen a spike in threats following the shooting, a common occurrence after school shootings, Jay Greenberg, special agent in charge of the St. Louis field office of the FBI, said at the news conference.

Greenberg said these threats are “typically easy to investigate” and police are able to quickly find who is making them. But because of the volume of the threats, authorities have increased police presence in schools across the St. Louis metro area as a precaution.