Federal investigators say a 49-year-old Billings man died earlier this month of injuries suffered when the barrel of a homemade cannon exploded at a residence east of Laurel.
    
The Billings Gazette reports (http://bit.ly/U7koud ) the results of an investigation by the Bureau of Alcohol, Tobacco, Firearms and Explosives were unsealed in U.S. District Court this week.
    
Billy J. Ullom died Dec. 1 from severe blood loss from shrapnel injuries. A witness told deputies that a group was firing rocks from the cannon when the 3-inch barrel exploded.
    
The owner of the cannon told the ATF he was a pipefitter and built the cannon about seven years ago. He said he had fired it about 150 times without any problems.
    
Assistant U.S. Attorney Jessica Fehr declined to comment on possible charges over the unregistered cannon.