A large truck tire exploded Saturday at an auto center in New Hampshire, killing a worker and seriously injuring a customer from Maine.

Police said they were called to the Sears Auto Center in Salem about 7:50 a.m.

According to a 911 call, a worker was filling up the tire when it “exploded off the machine” and hit both men in the head.

Police said the worker, Justin Almon, 22, of Sandown, died of head injuries. They said the customer, Adam Sproul, 23, of Boothbay, was flown to Boston Medical Center with serious head injuries.

Chris Sproul of Boothbay, Sproul’s grandmother, said late Saturday that he suffered a serious concussion but was stable.

“The next 24 hours are critical, that’s what they told us,” she said.

Salem police and the U.S. Occupational Safety and Health Administration are investigating the incident. Sears said in a statement that it’s working with authorities and extends its thoughts and prayers to both families. A sign outside the auto center in Salem said it was “closed for the day,” WCSH-TV reported.