A list of some school shootings and where authorities believe the students obtained guns:
Feb. 27, 2012: Seventeen-year-old T.J. Lane arrested following a multiple shooting in a school in Chardon, Ohio, outside of Cleveland. Three students died and two were wounded in the spree, which started in the school cafeteria as he and other students waited for buses to other schools. Authorities did not immediately say where they believe Lane got a .22-caliber handgun.
Feb. 22, 2012: A 9-year-old boy in Port Orchard, Wash., brought a .45-caliber handgun to his elementary school where the weapon discharged from inside his backpack, critically injuring 8-year-old Amina Kocer-Bowman. Authorities believe he got the weapon during a visit with his mother.
April 19, 2011: A 6-year-old boy accidentally fired a gun inside Ross Elementary School in Houston, Texas, injuring himself and two other children. The boy and his mother were staying at the home of Wrolandrea Hensley, 30, who had hidden the gun under a futon cushion. The boy found the gun on the floor. Hensley was charged with making a firearm accessible to a child.
March 25, 2011: Michael Phelps, 15, shot another student at Martinsville West Middle School in Martinsville, Ind. Phelps had stolen the 9mm handgun from a family friend's home.
Sept. 29, 2006: Eric Hainstock, 15, took a shotgun from his father's gun cabinet and a .22-caliber revolver from his father's bedroom to his school in rural Cazenovia, Wis., and fatally shot the principal.
March 21, 2005: With his own .22-caliber handgun, and his grandfather's Glock handgun and 12-gauge shotgun, Jeff Weise, 16, shot and killed his grandfather, a policeman and his grandfather's girlfriend at their home, then went to his high school, also on the Red Lake Indian Reservation in northern Minnesota, and fatally shot eight people, including himself.
April 24, 2003: James Sheets, 14, shot and killed principal Eugene Segro in the crowded cafeteria at the Red Lion Area Junior High School in south-central Pennsylvania before killing himself. Police determined that Sheets used a key to take three guns from his stepfather's gun safe.
May 26, 2000: Nathaniel Brazill, 13, killed his English teacher at Lake Worth Community High School in Lake Worth, Fla. According to police, Brazill stole the .25-caliber semi-automatic pistol from his grandfather's house.
Feb. 29, 2000: A 6-year-old boy from Mount Morris Township, Mich., killed classmate Kayla Rolland, also 6, at Buell Elementary School with a .32-caliber semiautomatic handgun left in an open shoebox. The boy and his mother had been staying at the home of his uncle and his uncle's friend, Jamelle James, 19. James, who kept the gun in the shoebox, spent 2 1/2 years in prison after pleading no contest to involuntary manslaughter.
Sources: Associated Press and other news reports.
Compiled by Associated Press news researcher Rhonda Shafner.