For the record: Timeline of tragedy

By most accounts, the deadly rampage at 1,900-student Columbine High School began about 11:15 a.m. on April 20-Hitler's birthday, as hardly anyone knew or cared. In long black coats, Eric Harris, 18, and Dylan Klebold, 17, approached from the soccer field, shooting at students and lobbing pipe bombs at cars in the parking lot. They shot into the windshield of Sheriff's Deputy Neil Gardner's Ford Bronco as he radioed for backup; he narrowly escaped injury or death. They fatally shot Daniel Rohrbaugh, 15; he was the boy in the green shirt television viewers nationwide saw lying crumpled on the sidewalk outside the rear entrance.

As students scrambled for their lives, the pair entered a hall and then the cafeteria, firing randomly and tossing more pipe bombs. Fire alarms and sprinklers came on. Amid the panic, screaming, and running, Rachel Scott, 17, fell mortally wounded in the hall.

At some point, the two traded shots with Deputy Gardner and two backup officers. The deputies retreated outside to await more help. "We were outgunned," the deputy explained to reporters later.

The pair walked upstairs to another hall and classrooms. They kept blasting away. Trying to protect students, David Sanders, 47, a science teacher and coach, suffered horrific chest and shoulder wounds. (A SWAT team officer cleared students from the area about 3:00 p.m., but it was another hour before police returned for Mr. Sanders; he had died in the meantime.)

The shooters entered the library, where four dozen students and workers, alerted by a teacher and the noises in the cafeteria below them, were seeking cover. Survivors said the pair were laughing and shouting taunts as they shot at their terrified victims. When it was all over-by noon, police believe-10 students and the two assailants lay dead in the library; others were wounded. A coroner later said the attackers died of self-inflicted gunshot wounds. Police, uncertain about how many gunmen or booby-traps they might encounter, did not pronounce the premises secure until about 4 p.m.

In all, 21 students were wounded, several seriously. (Nine were still hospitalized on April 28, two in serious condition and several with partial paralysis.) Medical workers cautioned it could take years for them and many of their more fortunate classmates to recover fully from the emotional wounds of that terrible day.