Authorities in Florida say the shooter opened fire at a high school Wednesday afternoon, killing at least 17 people. The shooting sent frightened students running out into the streets and SWAT team members swarming the building.
Here's a look at some recent U.S. school shootings, and some of the deadliest of years past:
Jan. 23, 2018: Two students were killed and 14 wounded by gunfire when a student opened fire before classes began at Marshall County High School in west Kentucky, authorities said. A grand jury is meeting to consider charging the 15-year-old boy as an adult.
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Dec. 7, 2017: Two students at Aztec High School in New Mexico were killed by a gunman disguised as a student. Police said the shooter later killed himself.
Sept. 13, 2017: A 15-year-old boy was killed at Freeman High School in Rockford, Washington, and three female students were wounded when authorities say another 15-year-old boy opened fire with a handgun. A suspect was arrested.
April 10, 2017: A gunman opened fire in the special education classroom of his estranged wife at North Park Elementary School in San Bernardino, California, killing her and an 8-year-old boy, and wounding another child. The gunman then fatally shot himself.
Sept. 28, 2016: A 6-year-old boy was fatally shot on the playground of Townville Elementary School in South Carolina by a 14-year-old boy who had just killed his father, authorities said. Another child and a teacher were struck by bullets but survived. The teen was charged with murder.
Sept. 8, 2016: A 14-year-old girl died of a self-inflicted gunshot wound after shooting and wounding another female student at Alpine High School in West Texas.
Dec. 14, 2012: A 20-year-old gunman killed 20 first-grade children and six educators inside Sandy Hook Elementary School in Newtown, Connecticut, and then killed himself. He also fatally shot his mother before entering the school.
Feb. 27, 2012: Three students were killed and two wounded in a shooting that started in a school cafeteria in Chardon, Ohio, as students waited for buses to other schools. Police charged a suspect, 17 at the time, as an adult.
April 16, 2007: Twenty-three-year-old Seung-Hui Cho fatally shot 32 people in a dorm and a classroom at Virginia Tech in Blacksburg, and then killed himself.
April 20, 1999: Students Eric Harris, 18, and Dylan Klebold, 17, opened fire at Columbine High School in Littleton, Colorado, killing 12 classmates and a teacher and wounding 26 others before killing themselves in the school's library.
Dec. 1, 1997: Three students were killed and five wounded at a high school in West Paducah, Kentucky. Michael Carneal, then 14, later pleaded guilty but mentally ill to murder and is serving life in prison.