The fire that killed a West Virginia Air National Guard firefighter early Sunday was arson, the states fire marshal said.
The firefighter, whose name has yet not been released, was responding as aid to a fire in Martinsburg, a city in the states northeast corner, according to NBC Huntington affiliate WSAZ.
Officials have said there were two arsons early Sunday, one at 2 a.m. that killed the firefighter and one earlier at around 1:30 a.m in neighboring Jefferson County.
The state fire marshal tweeted that the fires were set at unused structures about three miles apart.
The marshal had not yet publicly identified any suspects and was offering a reward for information leading to an arrest.
The deceased firefighter was assigned to the 167th Airlift Wing in Martinsburg. It was unclear if there were any additional injures from the arson.