Clinton, N.C. — Two men were arrested Wednesday after their homemade bomb exploded prematurely, injuring both, authorities said.

Acting on an anonymous tip, Sampson County deputies found a Chevrolet minivan outside Sampson Regional Medical Center with a side window blown out and blast marks on the outside of a door, authorities said.

Inside the hospital emergency room, Martin Bryant Boyette and Julio Frentez Morales were receiving treatment for injuries from a bomb blast, authorities said. An investigation determined that the pair had made several bombs at Boyette's house, where both lived, and Morales tried to throw one out the window of the minivan on U.S. Highway 701 as they drove past Hobbton Schools, authorities said.

The bomb went off in Morales' hand, seriously injuring him, and a piece of shrapnel hit Boyette in the back of the head, authorities said.

"It's scary to think that these individuals were going to throw an explosive device out of a vehicle in front of a school," Sampson County Sheriff Jimmy Thornton said in a statement. "What were they thinking? What possible thrill could be worth potentially injuring an innocent person, especially a child?"

The State Bureau of Investigation and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives were called in to assist with the case. ATF agents searched the minivan and determined no other bombs were inside, authorities said.

A pipe bomb was found during a search of the house, and the Cumberland County Sheriff's Office Bomb Squad responded to disarm it, authorities said.

Boyette, 34, of 1681 Keener Road, Clinton, and Morales, 25, of the same address, were each charged with one count of possession of a weapon of mass destruction. Boyette was being held in the Sampson County Detention Center under a $35,000 bond, while Morales had been released on bond.

The owner of the minivan, Lisa Ann Mooring, 35, who also lived at the Keener Road house, was charged with possession of methamphetamine and possession of drug paraphernalia after deputies found 2 grams of methamphetamine while interviewing her during their investigation of the bomb explosion. She was being held in the Sampson County Detention Center under a $200,000 bond.

The investigation also determined a third man was involved in the incident, and a search of another home turned up 1 gram of methamphetamine, authorities said. Allen Tart Bass, 38, of 307 Carr Church Road in Clinton, was charged with possession of methamphetamine and possession of drug paraphernalia and was being held in the Sampson County Detention Center under a $200,000 bond.

The ATF is investigating the case for possible federal charges, authorities said.