A Southern California man arrested on suspicion of having explosives after a blast killed his ex-girlfriend at her day spa has walked free after U.S. prosecutors said Tuesday that they had dropped the charge against him.

Stephen Beal was released from jail Sunday — a day after a judge approved prosecutors’ request to drop a single charge of possessing an unregistered destructive device, the U.S. attorney’s office said.

Beal, 59, was arrested during the investigation into the May 15 bombing that killed Ildiko Krajnyak in her Orange County spa, but he was never named as a suspect in the blast.

Federal investigators said they had discovered two improvised explosive devices, three firearms and more than 100 pounds of explosive material during a search that Beal allowed of his house.

Prosecutors dropped the charge after the FBI said it had questions about whether material found in the house met the legal definition of a “destructive device.”

Beal, a model-rocket hobbyist, told investigators he had not made any bombs and did not have material for an explosion as powerful as the one he saw in news coverage.

Krajnyak, 48, was killed and two female clients were seriously injured when she opened a box that erupted in a fiery explosion at the spa in the city of Aliso Viejo, about 50 miles south of Los Angeles, investigators said.

The curtains and blinds were drawn at Beal’s home in Long Beach, and he did not answer the door or return messages sent to him by friends on behalf of The Associated Press.

“I’m glad he’s home. I feel sorry for him,” said Don Westerhoff, who lives across the street. “You can be able to build rockets and not be able to build a bomb that’ll blow up in a box.”

Beal told investigators that he and Krajnyak had recently split up over issues of exclusivity and finances, according to an affidavit filed in court by an FBI agent. But they remained business partners.

Krajnyak, a mother and licensed cosmetologist, had just returned to California after visiting family in her native Hungary.

The Orange County district attorney’s office said it would provide an update on the investigation later Tuesday.