NASHVILLE, Tenn. (WKRN) – Metro police’s bomb squad assisted Vanderbilt neurosurgeons as they operated on a Rutherford County man who was critically injured in a fireworks accident.

Juan Diaz-Castrejon was playing around with fireworks Saturday night at a friend’s home when the commercial grade artillery shell exploded into his skull.

The 35-year-old man was severely injured in the accident.

“I thought he was going to die,” said friend Glen Salas. “Juan is a nice guy. Someone you want to hang out with, but sometimes he does crazy things.”

The accident happened after Diaz-Castrejon reportedly loaded a shell upside down and then held the tube above his head while attempting to blow off the shell.

“It looked like a war zone; something blowing up. You go get your buddy and he is not the same person,” Salas said.

The Rutherford County sheriff’s deputy who was the first on the scene reported Diaz-Castrejon had a severe skull fracture which was causing extreme blood loss and loss of brain matter.

Diaz-Castrejon was airlifted to Vanderbilt University Medical Center where the volatility of the injury caused doctors to call in Metro’s bomb squad.

An x-ray showed a two-inch shell in his skull. Due to concerns the shell might still explode, Metro police’s bomb squad was called in to assist.

“That is the first time I ever got that call,” said Gerry Gann with the bomb squad. “It is certainly one for the books.”

Gann said he scrubbed in and was present during the surgery in the event of an emergency.

“My concern was to avoid heat shock or friction while in the ER surrounded by multiple patients because those are the three main factors that would set off an explosive device,” explained Gann.

It was ultimately determined the artillery shell that pierced Diaz-Castrejon’s skull was not explosive.

“Yes, many times I was thanked by hospital staff and administrators for being there and giving technical device,” Gann said.

Salas told News 2 his friend is making a “remarkable recovery.”

Diaz-Castrejon is alert and reportedly giving people the thumbs up sign and holding loved ones hands.

Salas said he plans to take the unexploded fireworks to his local fire station, adding he thinks it could serve as a warning to all kids not to fool around with fireworks.