Until Wednesday, there had been one fatal shooting at U.S. schools this year, the Jan. 23 killing of two students at Marshall County High School in Kentucky.
That was before a gunman opened fire inside classrooms at Marjory Stoneman Douglas High School in the Miami suburb of Parkland, killing 17 people.
It was a return to normal for America.
There have been 290 school shootings in the United States since 2013 — or more than one a week — according to Everytown for Gun Safety, a nonprofit that advocates for gun control. Its tally includes college campuses and all incidents in which a gun was fired, regardless of whether anybody was killed or injured.
In the majority of school shootings, nobody is killed, and so they receive little media attention. Even the January shooting in Kentucky in which two 15-year-olds died received scant national coverage.
The Florida massacre was the 18th U.S. school shooting this year, according to Everytown. The scenes that played out on television Wednesday were familiar ones: students running with their hands clasped above their heads, crying parents hugging children, police huddled outside gymnasiums.
There have been shootings at schools since the 1800s, but the current trend appears to have started in the 1990s. The most notorious of those occurred in 1999 at Columbine High School in Littleton, Colo., when two students killed 12 classmates and a teacher.
The deadliest shooting at a primary or secondary school happened in 2012, when a gunman killed his mother, then went to Sandy Hook Elementary School in Newtown, Conn., and shot 20 first-graders and six adults.