Police shot and killed a student outside a middle school in Wisconsin on Wednesday after receiving a report of someone with a weapon, the state's attorney general said in the first law enforcement briefing on gunshots that sent children running and prompted an hours-long lockdown of local schools.

An active shooter who never entered the building, according to authorities, was "neutralised" outside of Mount Horeb Middle School. Josh Kaul, the state attorney general, informed reporters on Wednesday night that there had been no injuries and that the investigation was still ongoing.

“This incident took place outdoors. The subject in this case never gained entry,” he said. The student was identified by the authorities as a juvenile male, but they withheld his age and the school in the Mount Horeb district he attended.

Regarding what transpired after the police arrived, Kaul refused to comment on whether the student had fired a weapon, what kind of weapon he was carrying, and whether he attempted to enter the school. Authorities said that several Mount Horeb officers had fired weapons while wearing body cameras, but they did not specify how many.

After the incident, police stayed at the scene for hours, keeping students confined to buildings until late in the afternoon before gradually releasing them to their families.

The wait was tense and unsettling for parents and panicked children. Parents told stories of kids hiding in closets and afraid of talking on their phones. A middle school student said his class initially fled the school gym on in-line skates.

All district schools were placed on lockdown, according to the district's first Facebook post, which was made at 11:30am. The "alleged assailant" was the only person hurt, according to Mount Horeb authorities, although witnesses reported hearing gunshots and seeing dozens of kids running.

After several hours, police tape encircled the middle school, the neighbouring high school, and the playing fields that separated the two buildings. School buses were still parked in a line that extended blocks outside the middle school.

Around noon, a post stated, “An initial search of the middle school has not yielded additional suspects. As importantly, we have no reports of individuals being harmed, with the exception of the alleged assailant.”

Earlier, the district posted, without providing further details, that "the threat has been neutralised outside of the building" in Mount Horeb, a small village located roughly 25 miles (40 kilometres) west of Madison, the state capital.

A middle school student reported that during their in-line skating class in the school gym, they heard gunshots.

Twelve-year-old Max Kelly claimed his teacher ordered the class to leave. He claimed that after skating to a street and ditching their in-line skates, they sprinted to a convenience store and gas station nearby, where they hid in the restroom. Reunited with his parents, Kelly sat on a hillside with them early on Wednesday afternoon, waiting for his younger siblings to be released from their schools.

“I don’t think anywhere is safe anymore,” said his mother, 32-year-old Alison Kelly.

In the early hours following the incident, Mount Horeb police stated they were unable to provide any information.

Every school in the country has looked into ways to stop mass shootings within its walls, from technology, such as detailed digital maps, to physical security measures and active shooter drills. Many also depend on educators and administrators to identify early indicators of mental health issues in students.

According to Superintendent Steve Salerno of the Mount Horeb Area School District, "this could have been a far worse tragedy" in the absence of recent security upgrades. He did not provide further details, only stating that students reported seeing someone suspicious outside the building to the school staff right away.

“It’s an experience that you just pray to God every day that you just don’t ever have to enter into,” Salerno told reporters.

About 7,600 people live in the village, which also serves as the headquarters for outdoor retailer Duluth Trading Company. Because there are troll sculptures all over its downtown area, Mount Horeb bills itself as the "troll capital of the world."