The deadliest mass shootings in recent history have had one thing in common: the perpetrator used an assault rifle.

Why it matters: These weapons possess an incredible amount of killing power, and amplify the destructive will of the person who carries out an attack. Nine people died and 27 were injured in a mass shooting in Dayton, Ohio in an attack that lasted 32 seconds. The killer used an AR-15 style assault rifle.

Since 1999, there have been 115 mass shootings (defined below) in which 941 people were killed and 1,431 were injured.

there have been 115 mass shootings (defined below) in which 941 people were killed and 1,431 were injured. Of those 115 attacks, 32 — just over a quarter — involved semi-automatic rifles. But those attacks accounted for 40% of all deaths and 69% of all injuries.

115 attacks, 32 — just over a quarter — involved semi-automatic rifles. But those attacks accounted for 40% of all deaths and 69% of all injuries. Since 2017, 12 of the 31 mass shootings involved assault rifles — which caused 39% of the deaths and 92% of the injuries.

12 of the 31 mass shootings involved assault rifles — which caused 39% of the deaths and 92% of the injuries. That includes the Las Vegas massacre — which alone accounts for almost 40% of all mass shooting injuries since 1999. The perpetrator of that shooting used over 20 assault rifles during that attack.

About the data: This chart uses Mother Jones' dataset on mass shootings, which tracks the events since 1982. Our analysis is focused on shootings since 1999 — the year Columbine took place.