Until yesterday, the Columbine High School shooting of 1999 was the most infamous and shocking of the many gun attacks on American schools. The Virginia Tech massacre surpasses it in both scale and horror.

Bath, Mich., 1927

Forty-five died in a series of bombings at the Bath School in Bath Township, Mich. Most of the victims were young children. The killer, Andrew Kehoe, a school board member, was upset by a property tax levied to pay for the school.

Texas, 1996

Charles Whitman climbed a 27-story tower at the University of Texas at Austin and shot passersby on the campus before being killed by police. Fifteen died, including the shooter’s mother and wife, whom he had shot the night before. He had been suffering from a brain tumor.

Westside, Ark., 1998

At Westside Middle School in Jonesboro, Ark., two boys, 11 and 13 years old, set off the fire alarm and killed four students and a teacher as they left the school.

Columbine, Colo., 1999

Teenagers Eric Harris and Dylan Klebold rampaged through their school in Littleton, Colo., killing 12 students and one teacher, as well as wounding 24 others, before committing suicide. Videos were found of them testing an array of weapons and Harris’s diary contained the words: “So many people have to die.”

Red Lake, Minn., 2005

Jeffrey Weise, a 16-year-old student, shot five students, a teacher, and a security guard at Red Lake High School, northern Minnesota, before killing himself. Calling himself the Angel of Death on neo-Nazi Web sites, he also killed his grandfather and the man’s girlfriend on the Chippewa Indian reservation.

Bailey, Colo., 2006

Duane Morrison, a 53-year-old drifter, took six female high school students hostage in Bailey, Colo., after entering Platte Canyon High School, claiming to be carrying a bomb. He sexually assaulted them and then shot one, fatally, before killing himself.

Nickel Mines, Pa., 2006

Charles Roberts, 32, a milk truck driver, entered the wooden, one-room Amish school in Nickel Mines, a village in Pennsylvania, and took everyone hostage. He bound and then shot 10 girls between the ages of 7 and 13, killing five, before shooting himself. Roberts had indicated that he had had dreams about molesting children.