GILLETTE, Wyo. (AP) — Authorities say a 14-year-old northern Wyoming boy was killed when the cannon he was building exploded.

Campbell County Sheriff Scott Matheny tells the Gillette News Record that Archie Pearce was making the cannon in an abandoned lot in Recluse and was showing it to a 12-year-old friend when it misfired Thursday evening.

The boy had used a steel pipe, cloth and gun powder or firework powder to build the cannon, but he packed too much powder into the device. Because the pipe was packed too tightly, the projectile inside became stuck, causing an explosion.

Investigators say the boy was learning how to make the cannon based on online videos.

Bomb technicians called to the scene did not find any other dangerous devices.

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Information from: The Gillette (Wyo.) News Record, http://www.gillettenewsrecord.com