Witnesses spot Kriegman's gray 1991 Pontiac Grand Am. It is presumed that Calvin Gabriel and Andre Kriegman are both in the car at this time. They turn off a video camera they have brought with them. Their whereabouts are not known for certain for the next hour and thirteen minutes.
Kriegman and Gabriel turn on their video camera, retrieve their weapons from the trunk. They spend approximately 5 minutes loading their weapons and proceed towards the west entrance of Iroquois High School.
10:02:10 AM - 10:02:17 AM
As Kriegman and Gabriel approach the west entrance, they encounter Melissa Baker, Jason Zuffoletti, and Tony DeFasio, who are sitting to the left of the entrance. Kriegman and Gabriel fire upon the students. All three are hit; Zuffoletti and Baker are killed instantly, and DeFasio is able to flee. Robert Straitharn comes through the main entrance and is wounded by Kriegman. He turns around and runs back into the school. James Regent, Michael Oster, Jennifer DiCaprio, Alison Stewart, and Kristin Powers are also outside, around the corner to the left of the main entrance, in a courtyard with walls on three sides. When the shooting starts, they make their way to the wall farthest from the main entrance and run. After firing at Straitharn, Kriegman and Gabriel turn their attention to the group coming out of the cul-de-sac. Kriegman wounds Oster and Dicaprio, and Powers is hit by Gabriel in the leg. Kriegman and Gabriel pause to reload, and Regent and Stewart take this opportunity to assist Powers. Kriegman and Gabriel lose interest in this group, and opt to enter the school.
10:02:20 AM - 10:02:35 AM
Kriegman and Gabriel enter the school and encounter Resource Officer Leon Stetz. Witnesses observe Stetz issue a warning and draw his weapon. Kriegman and Gabriel and Stetz exchange fire. Stetz fires three rounds and is hit three times by Gabriel. Stetz dies of his wounds before aid can arrive. Stetz's revolver is later found sabotaged, presumably by Kriegman or Gabriel; a safety pin is inserted in the breech. It is not clear when this was done.
10:02:20 AM - 10:02:35 AM
After the exchange with Stetz, Kriegman and Gabriel proceed towards the library, firing on the students in the hall who, by now, have already started to flee. Timothy Pastor, James Woodruff, Denise Kelso, and Lisa Chang are hit, but are able to flee the scene.
Students in the west of the library observe Kriegman and Gabriel through the library's east entrance and start to rush towards the main entrance. Others in the main entrance of the library follow them. The students at the front of the crowd see Kriegman and Gabriel approaching and change direction followed by the rest of the students. Kriegman and Gabriel wait until they are in through the doors and open fire. Victoria Evers and Omar Walters are hit; Evers dies of her wounds before aid can arrive. Omar, who has called 911 shortly before Kriegman and Gabriel arrive, is able to move into the reference area with other fleeing students. The larger group of students escapes through the west entrance. Kriegman picks up the cellular phone that Walters used to call 911. The phone will remain with Kriegman and continue to transmit until the SWAT team arrives.
A group of approximately thirty students moves east to the reference area while Kriegman and Gabriel are occupied in the main area. Walters cannot keep up with the rest of the group and sits down. At this point the group splits up again. One group moves upstairs to a study room, while the second group makes it way to an emergency exit. Worried that the alarm on the emergency exit might draw Kriegman and Gabriel, they force a window open and jump down 4 feet to escape.