Records show 70% of school shootings since 1999 have been carried out by people under 18: report

• Seven in 10 school shootings in the US were carried out by children under 18, The Washington Post reported.
• The Post's analysis only factored in incidents where the shooter's age was known.

At least 70% of all school shootings since 1999 have been carried out by people under the age of 18, when counting cases where the age of the shooter was recorded, The Washington Post reported.

The youngest of these was a six-year-old male first grader, who shot his classmate in 2000 with a .32-caliber handgun after saying he didn't like her.

Based on incidents during that period, the median age of school shooters on K-12 campuses is 16, excluding 86 cases where the shooter's age is unknown, per The Post.

In cases where the source of the firearm used could be determined, more than 85% of shooters brought them from home or got them from friends or relatives, The Post reported.

Combined, the figures point to the role adult negligence has played in allowing underaged children to obtain lethal firearms.

One of the deadliest attacks happened on Tuesday — a shooting at Robb Elementary School in Uvalde, Texas. At least 19 children and two adults had died as of Tuesday night.

The suspect was an 18-year-old local resident, who was shot dead by a border patrol officer who rushed into the school without backup and was wounded in the process, a law enforcement officer told The Associated Press. Authorities told the Houston Chronicle the suspect purchased the two AR-15-style rifles the day after his 18th birthday.

According to The Post, 311,000 children in 331 schools have been exposed to gun violence in their schools since the 1999 Columbine High shooting.

The outlet reached these figures by aggregating records from news reports, open-source databases, law enforcement reports, and calls to schools and police departments, it said.

The Post's findings only factor in gunfire incidents that happened on campus immediately before, during, or just after classes, and excluded shootings at colleges or universities. It also excluded shootings after hours or accidental discharges where no one was hurt.