The set of statistics below comes from Ohio Trainer Robert Borsch who is a proponent of single officer entry on active shooter incidents when that is all that is available. These statistics were published in the latest edition of the Force Science Newsletter:

From reviewing close to 100 active-killer outbursts, Borsch has found (in rounded figures) that: 

• 98% of the offenders act alone 
• 90% commit suicide, usually on-site (with most exceptions seeming to occur in cases with domestic-violence overtones)
• 80% use a long gun (rifle, shotgun, or carbine of pistol caliber)
• 75% bring multiple weapons to the scene, sometimes with hundreds of rounds of ammunition
• the offenders typically are "preoccupied with a high-body-count plan, racing to complete it and avoid police"
• increasingly, they are wearing body armor
• they almost never take hostages and do not negotiate
• they are "dynamic and quick," finishing their slaughter in a post-Columbine average of 8 minutes. 

Click here to download the School Shooter: Quick Reference Guide from the FBI

Hit the "Read More" link for the full article from the Force Science Research Center.