Early this morning, at least 10 people were shot and killed at Santa Fe High School near Galveston, Tex.

The incident is the second school shooting in the United States this week, according to a Washington Post database of school shootings. After the Feb. 14 school shooting in Parkland, Fla., a new generation of student activists vowed “never again.” The Santa Fe shooting is the 10th school shooting since then.

The Washington Post's database has tallied 220 school shootings since the April 1999 shooting at Columbine High School in Littleton, Colo. 2018 is shaping up to be the worst year for school shootings in America in The Post's database: The 16 shootings that have occurred this year tie 2018 with 2014 for the largest number of shootings in a given year. It is only May.

The Post database includes every discharge of firearms at a primary or secondary school during school hours. As such, its overall tally is lower than some other counts of school shootings, which include events that happen after school hours. The Post database does not include accidental discharges of firearms that injure nobody beyond the person handling the gun. Injuries or fatalities to the shooters are also not included in the tally.

The 220 shootings have occurred at schools in 40 states plus the District of Columbia.

There's no immediately discernible geographic pattern to the shootings. Most have occurred in high-population states, such as California, Florida and Texas. New York, however, stands out for having a high population (it's the fourth-most-populous state in the nation) and a low number of school shootings (three). Louisiana has seen more than three times as many school shootings as New York, despite having less than one-quarter of the population.

Roughly one-quarter of the school shootings in the Post database involve no injuries or fatalities to students. But that doesn't mean that students weren't in mortal danger. Earlier this week, just such a shooting occurred at Dixon High School in Illinois, when authorities said a former student walked into a school and began shooting near the gym. He was chased off by an armed school resource officer before any students were injured.

While the injured and dead are still being counted in Santa Fe, preliminary tallies by local authorities would place the incident as the nation's fourth-deadliest school shooting, following only by Columbine, Parkland and Newtown, Conn.