A look at some of the deadliest US school shootings


              FILE - A family visits the memorial crosses dedicated to the the 13 people killed in the 1999 Columbine High School shooting attack, at Chapel Hill Memorial Gardens in Littleton, Colo., Easter Sunday, April 20, 2014. There have been dozens of shootings and other attacks in U.S. schools and colleges over the years, but until the massacre at Colorado's Columbine High School in 1999, the number of dead tended to be in the single digits. Since then, the number of shootings that included schools and killed 10 or more people has mounted .(AP Photo/Brennan Linsley, File)
            
              FILE - Jillian Soto, center, thanks the hundreds of people who came out to attend a candlelight vigil in memory of victims from the mass shooting in Newtown, Conn., which was held behind Stratford High School on the Town Hall Green in Stratford, Conn., Dec. 15, 2012. Jillian's sister Vicki, a Stratford native, was a teacher at Sandy Hook Elementary School and was one of the victims in the shooting. There have been dozens of shootings and other attacks in U.S. schools and colleges over the years, but until the massacre at Colorado's Columbine High School in 1999, the number of dead tended to be in the single digits. Since then, the number of shootings that included schools and killed 10 or more people has mounted. (Christian Abraham/Hearst Connecticut Media via AP, File)
            
              FILE - Lillie Perez, 11, holds a sign during a "March for Our Lives" protest for gun legislation and school safety March 24, 2018, in Houston. Students and activists across the country planned events Saturday in conjunction with a Washington march spearheaded by teens from Marjory Stoneman Douglas High School in Parkland, Fla., where over a dozen people were killed in February. There have been dozens of shootings and other attacks in U.S. schools and colleges over the years, but until the massacre at Colorado's Columbine High School in 1999, the number of dead tended to be in the single digits. (AP Photo/David J. Phillip, File)
            
              FILE - Marjory Stoneman Douglas High School administrative employees Margarita LaSalle, left, and JoEllen Berman, walk along the hill near the school lined with 17 crosses to honor the students and teachers killed on Valentine's Day, as teachers and staff returned to the school, Feb. 23, 2018, in Parkland, Fla. There have been dozens of shootings and other attacks in U.S. schools and colleges over the years, but until the massacre at Colorado's Columbine High School in 1999, the number of dead tended to be in the single digits. Since then, the number of shootings that included schools and killed 10 or more people has mounted. (Charles Trainor Jr/Miami Herald via AP, File)
A look at some of the deadliest US school shootings