When and where America’s mass shootings have occurred in 2018

Combined ShapeCaption
VIDEO: Survivors of Las Vegas Shooting Were at California Bar Shooting

The Wednesday night massacre in Thousand Oaks, California, is the 307th mass shooting in the United States this year, according to the Gun Violence Archive.

» RELATED: Thousand Oaks shooting: 12 killed, including deputy, at California bar; suspect also dead

The not-for-profit organization offers public access to data on gun-related violence and identifies mass shootings as incidents in which four or more people were shot or killed, not including the shooters.

"But 'mass shooting' is a term without a universally-accepted definition," the Washington Post reported in 2015, after 14 people were shot and killed in San Bernardino, California:

"The FBI does not officially define 'mass shooting' and does not use the term in Uniform Crime Report records," according to the Post's Fact-Checker. "After the 2012 shootings in Newtown, Conn., Congress defined 'mass killings' to mean 'three or more killings in a single incident.' Some media outlets and researchers still use the four-fatality definition, and have adopted the CRS definitions of 'mass shooting' and 'mass public shooting.' Other researchers include injuries in the victim count. Some researchers include acts of terrorism, drug deals gone wrong or gang conflict in their research. Others don't."

» RELATED: Questions, answers on American mass shootings

The tragedy in Thousand Oaks unfolded late Wednesday when a gunman opened fire at a local bar during its college night. Twelve people, including a sheriff’s deputy, were killed. The shooter is also dead. Just three weeks earlier, eleven people were killed and six wounded during a bloodbath at the Tree of Life synagogue in Pittsburgh.

The California city is known for consistently ranking among America's safest cities.

» RELATED: Thousand Oaks shooting: Tamera Mowry-Housley, Adam Housley confirm niece died at Borderline Bar

“I never thought I would see the things around the country that would happen, but I’ve learned it doesn’t matter what community you’re in,” Ventura County Sheriff Geoff Dean said during a press briefing after the shooting. “It doesn’t matter how safe your community is; it can happen anywhere.”

Per the Gun Violence Archive’s definition, a total of 328 people have died in the 307 mass shootings this year. Another 1,251 were injured.

» RELATED: How to cope with fear, sadness after a mass shooting

Using Congress’ definition of “mass killing” — three or more homicides in a single incident — there have been 39 incidents so far this year.