The 9mm handgun reportedly used by the 6-year-old Virginia boy who shot his teacher was legally purchased by his mother, police revealed. 

Additional details about the school shooting that injured teacher Abby Zwerner, 25, were brought to light during a Monday news conference.

The boy took the firearm from his home to school in his backpack on the day of the shooting. 

"What we know today is that she was providing instruction. He displayed a firearm, he pointed it, and he fired one round," Newport News police Chief Steve Drew said.

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Drew had previously said that the shooting was not accidental and had declined to elaborate, but said he wanted to clarify the remarks he made just after the shooting on Friday when he said there was an "altercation" between the boy and first-grade teacher. Rather, he said it was more like an "interaction" between the two before the shooting at Richneck Elementary School.

Zwerner put up her hand in a defensive position when the gun fired, and the bullet went through her hand and into her upper chest, Drew said. Although her injuries were initially considered life-threatening, her condition has improved, and she is currently listed as stable at a hospital.

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The police chief hailed Zwerner a hero for quickly hustling her students out of the classroom even after being shot. He said surveillance video shows she was the last person to leave her classroom.

"She made sure every one of those kids were out of that room. She was the last one to leave … after suffering a gunshot wound, to make sure her students … were safe," Drew said.

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A school employee reportedly rushed into the classroom and physically restrained the boy after hearing the gunshot. The boy became "a little combative" and struck the employee, Drew said. He was escorted out of the building and into a police car after officers arrived.

The boy has been held at a medical facility since an emergency custody order and temporary detention order was issued Friday, Drew said. He said it will be up to a judge to determine what the next steps are for the boy. He also said the boy’s mother has been interviewed by police, but it is unclear whether she could potentially face any charges.

"Drew says the gun was legally purchased in York County by the child’s mother. It’s still unclear how the student got ahold of the gun and brought it into Richneck Elementary. Drew says only one round was fired, but multiple rounds were inside the gun’s magazine. Authorities also seized a cell phone and a backpack from the scene," WAVY-TV reports. 

Gun owners can be prosecuted under a Virginia law that prohibits anyone from recklessly leaving a loaded, unsecured gun in a manner that endangers the life or limb of children under 14. A violation of that law is a misdemeanor, punishable by a maximum jail sentence of one year and a maximum fine of $2,500.

Virginia does not have a law that requires unattended guns to be stored in a particular way or a law that requires gun owners to affirmatively lock their weapons.

Legal experts said even though it is theoretically possible under Virginia law to criminally charge a 6-year-old child, there are numerous obstacles to doing so and it’s highly unlikely that any prosecutor would even try.

To be tried as an adult in Virginia, a juvenile must be at least 14. A 6-year-old is also too young to be committed to the custody of the Department of Juvenile Justice if found guilty. In addition, a common law doctrine known as the "infancy defense" holds that children under 7 cannot be prosecuted for a crime because they are so young that they are incapable of forming criminal intent.

A judge would also have to find that the child was competent to stand trial, meaning that he could understand the legal proceedings against him and assist in his own defense, said Andrew Block, a professor and the University of Virginia School of Law who was the director of Virginia’s Department of Juvenile Justice from 2014 to 2019.

"It’s virtually impossible to imagine a 6-year-old being found competent to stand trial," Block said.

Classes have been canceled at Richneck Elementary School through Friday. 

Families are invited to participate in a virtual town hall at 6:30 p.m. Thursday as school officials plan for students' return to the classroom, according to WAVY. A registration link will be emailed to all Richneck families on Tuesday. 

Fox News' Sarah Rumpf and the Associated Press contributed to this report.