Parents in the Wisconsin village of Mount Horeb got a terrifying alert from their children's school in May: There was an active shooter on campus.

But unlike tragedies that unfolded in places like Newton, Connecticut and Uvalde, Texas, police were able to stop the shooting before it started. They fatally shot an armed boy outside the school, and no one else was injured.

The close call is among dozens of what the Federal Bureau of Investigations defines as an "active shooter incident" in the United States. While such incidents can turn into mass shootings, the FBI's tracking includes the averted disasters, as well.

In a new report about active shooter incidents in the U.S., the agency found that though they went down slightly in 2023 from the previous year, more people were killed by active shooters than in 2022.

There were 48 active shooter incidents in the U.S. in 2023, down from 50 in 2022. But active shooters killed 105 people in 2023, compared to 100 such killings in 2022, the FBI said.

Where did active shootings occur in the U.S.?

California experienced the most active shootings in the U.S., followed by Texas.

An active shooter is defined as “one or more individuals actively engaged in killing or attempting to kill people in a populated area," according to the FBI.

Twenty-six states reported active shootings last year. Eight active shooter incidents were reported in California , with 47 people killed. Maine had the highest number of casualties in its one active shooting incident last year; 18 people were killed and 13 others were injured.

Active shootings identified by the FBI do not involve self-defense, gang violence, drug-related violence, residential or domestic disputes or hostages.

The report does not include when a shooter harms themselves, nor shootings that were the result of another unrelated crime.

Where did active shootings occur?

The FBI found that 28 of the 48 active shootings occurred in open spaces such as urban spaces or parks.

More people were killed in active shootings that occurred in commerce spaces, such as malls, compared to any other location. About 130 people were killed or wounded in 14 shootings that took place in a commerce space in 2023, the FBI says..

Varying definitions of mass shootings

It's important to note that the definition of mass shootings varies and other groups have death counts that veer wildly from the FBI's.

For instance, the FBI said active shooter incidents killed 103 people in 2021. But an online database called the Gun Violence Archive, which defines mass shootings as involving four or more victims, found that 706 people were killed in such attacks in 2021, according to the Pew Research Center.

Gun violence declared a national health crisis

Last month, the U.S. surgeon general declared gun violence a public health crisis, issuing an advisory on initiatives to prevent firearm deaths. The advisory said the rate of firearm-related deaths “reached a near three-decade high in 2021."

According to U.S. Surgeon General Vivek Murthy, more than 48,000 people died by gun violence in 2022, that's an increase of 16,000 deaths compared to 2010. At the same time, firearm-related suicides have increased by 20%, including a “staggering increase” in such deaths among young people, the advisory noted.

Murthy said gun violence demands a public health approach rather than the polarizing political response.

Gun violence became the leading cause of death in children and U.S. adults are worried that they or a loved one will become a victim, according to Reuters. More than half of U.S. adults said that they or a family member experienced a firearm-related incident, a 2023 report from Kaiser Family Foundation found.