Bomb Summary

On April 20, 1999 the Jefferson County Bomb Squad responded to Columbine High School because of reports of explosive devices being used during the shooting rampage. Shortly after, a metro-wide "all call" was initiated requesting assistance from local, state and federal agencies.

Explosives Experts

Bomb squad technicians from the Jefferson County Sheriff’s Office conducted the investigation of the various explosive devices. They were assisted by bomb technicians from the Arapahoe County Sheriff’s Office, Denver Police Department, Federal Bureau of Investigation (FBI) and the Bureau of Alcohol, Tobacco and Firearms (ATF). Approximately 33 people assisted in the bomb investigation. Sixteen were certified bomb technicians and the remainder were bomb-dog handlers, explosive recognition experts or evidence collection personnel from the FBI and ATF.

Diversionary Bomb 

Prior to the shootings at Columbine High School, a diversionary bomb exploded on the greenbelt near the 7900 block of South Wadsworth Boulevard. The Jefferson County Sheriff’s Office was notified of the explosion at 11:21 a.m. The Littleton Fire Department responded and West Metro Fire Department Investigator Bill Maron completed the investigation. The investigation revealed that two backpacks containing explosive diversionary devices, built with multiple components, had been placed at this location by Eric Harris and Dylan Klebold. Only some of the components actually exploded.

The examination of the diversionary devices by bomb technicians provided immediate critical information about the sophistication of the devices and the possibility of motion activators attached to the bombs. That information was relayed to the command post, the SWAT teams and the bomb technicians responding to the scene at the high school.


Beginning with an initial sweep of Columbine High School, the highest priority for removal of devices initially was given to the library so that the bodies of the deceased could be removed from the scene. Second priority would be given to the cafeteria and additional areas would be assessed. This plan was followed until two bombs, with timing devices attached, were found at 5:43 p.m. in two vehicles parked in the south student parking lot, a BMW belonging to Klebold and a Honda belonging to Harris.

As a result of these bombs, priority was changed with attention given first to the vehicles with the known timing devices. Bomb technicians, in bomb suits or using a remotely controlled robot, removed the bombs from these two vehicles in the school parking lot.

Before the school could be deemed clear and safe, every room, every storage area, every space on both levels of the 250,000-square-foot school was checked by bomb technicians.

A total of 1,952 student school lockers and 700 backpacks were checked for evidence of any type of explosive device. This process took approximately seven days from the time the incident began until the school was determined to be completely clear, thus allowing unrestricted access into the school by authorized personnel.

There were approximately 357 pieces of explosive evidence identified and collected. The bulk of this evidence was packaged and released on scene to ATF for additional testing and reconstruction as required.


During the collection and handling of the explosives evidence Tuesday evening, one bomb and other devices within the bomb trailer were accidentally detonated. Two bomb technicians from the Arapahoe Sheriff’s Office were lowering a pipe bomb into the trailer when a striking match attached to the pipe bomb brushed against the trailer wall and ignited. The devices exploded within the confines of the trailer. At 10:40 p.m. April 20, the radio report of --officer down-- stunned the entire law enforcement community responding to the Columbine incident. Thankfully, no one was hurt because the technicians were well trained and wearing protective bomb suits and knew to fall backward as they saw the spark from the device.

There were no injuries and no fatalities as a result of any bomb explosions.

Explosive Devices 

The subsequent investigation revealed numerous types and amounts of "improvised explosive devices," or self-made bombs. A device that had more than one component was still counted as one so as not to confuse how many separate bombs there were. For instance, the large propane tank bomb in the duffel bag contained multiple components but was counted as one bomb.

All of the improvised explosive devices that functioned were located at Columbine High School with the exception of the two pipe bombs used as a diversion. There were additional unexploded devices located at Columbine High School as well as the vehicles and residences of Harris and Klebold. Below is a list of where all the devices were located:


There were a total of 76 devices found at the school, two diversionary devices, 13 devices in the suspects’ cars, and 8 more at their two homes or a total of 99 explosive devices.

The investigation determined that Harris and Klebold placed two 20-lb. propane tank bombs in the cafeteria the morning of April 20. Computer modeling substantiated by field testing indicated that had those two large 20-lb. propane bombs detonated with a cafeteria full of students, most would have been killed or severely injured by the resulting blasts and subsequent fireballs. There were approximately 488 students in the cafeteria at 11:17 a.m. on April 20, the time the bombs were set to detonate. In addition to the casualties caused by the explosions, the computer models demonstrated a strong likelihood of structural damage and partial collapse of the cafeteria and possible library above.

During a search of the Harris residence, three significant homemade videotapes were found. One tape, shot in 1999, includes a section in which Harris and Klebold video tape their "arsenal" at the Harris residence. The video shows about 21 pipe bombs of varying sizes. The video also shows CO2 cartridge bombs, which Harris refers to as "crickets" and "grenades." Harris says there are 29.

Another tape, made in April of 1999, includes Harris and Klebold discussing making bombs and mentions propane and napalm. In addition, a spiral bound journal was recovered from the Harris residence that contains reference to bombs. One such entry, dated April 3, 1999, reveals "...we have six time clocks ready, 39 crickets, 24 pipe bombs, and the napalm is under construction." Another page that is not dated appears to be an inventory of bombs and indicates there are 53 of what Harris termed "crickets"and "super crickets" and 24 pipe bombs of different sizes.

Several leads were followed in an attempt to identify components and sources of the various devices and containers. Although some items were tracked through receipts, many items were found to be available at numerous retailers. In viewing the videotapes, there are indications of where some items were purchased. Additional information was found in Harris’ journal, a Day Timer, calendar pages, and a calendar taken from the Harris residence.