An 18-year-old who triggered a bonfire explosion that injured more than a dozen people at a backyard gathering in eastern Wisconsin has been sentenced to a year in jail and five years probation. WLUK-TV reports that Sam Armstrong appeared Thursday in Shawano County Court. Armstrong pleaded no contest in February to 13 counts of injury by negligent use of an explosive. Authorities have said Armstrong was attending a bonfire on Oct. 14, 2022, with other teenagers in Maple Grove when he threw a barrel containing a mix of gasoline and diesel into the fire, sparking an explosion that burned at least 17 of the roughly 60 youths who were there.