A Long Beach man and model rocket hobbyist has been arrested in connection with an explosion at an Aliso Viejo day spa last year that killed his ex-girlfriend and seriously injured two clients, federal authorities said Monday.

Nearly a year after the blast killed 48-year-old Ildiko Krajnyak, federal agents flooded Stephen Beal’s quite East Long Beach neighborhood on Sunday and arrested him on suspicion of malicious destruction of a building resulting in a death. Beal, a 59-year-old bit-part actor, faces a possible life sentence if convicted.

FBI has street roped off near Stephen Beal’s home off Volk Ave. pic.twitter.com/SC3L69zMZq — Kelly Puente (@KellyPuenteLB) March 4, 2019

In a news conference Monday, FBI officials said Krajnyak on May 15 was inside her day spa business when she opened a cardboard box that erupted into a fiery explosion. The bomb blew out part of the building.

Shorty after, authorities searched Beal’s home and arrested him on suspicion of possessing explosives, but he was later released after questions were raised over whether the material found in his home met the legal definition of a “destructive device.”

At the time, investigators said they found two improvised explosive devices, three firearms and more than 100 pounds of explosive material during a search that Beal allowed of his house.

Beal, 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.

Authorities on Monday said they now believe they have enough evidence in the case.

“The FBI and the Orange County Sheriff Department brought full forensic resources to bear on the case in order to process an enormous amount of evidence,” said Paul Delacourt, assistant director in the FBI’s Los Angeles field office.

Among the evidence, authorities found bits of wire similar to material at the explosion site in Beal’s home. Authorities said they also detected chemicals in his car that were similar to those at the explosion scene and have surveillance video of Beal at the scene days before the explosion.

Eight days before the blast, Beal bought cardboard boxes similar to the box his ex-girlfriend opened, authorities said.

On Monday, the street near Beal’s home remained blocked off as the FBI investigated.

Friend and neighbor Steve Young said Beal was a “good neighbor” who frequently worked on model rockets in the driveway. Young said he’s shocked at the allegations.

“He was a quiet person, I’d never seen him visibly angry with anyone,” Young said. “It seems very difficult to picture.”

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. The two remained business partners.

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

Following Krajnyak’s death, authorities raised new questions surrounding the death of Beal’s wife Christine Beal, who died in 2008 a few weeks after she fell down a flight of stairs while carrying a heavy piece of furniture with her husband.

The Los Angeles County coroner’s office said it was not clear if the death was related to trauma, but said there were no signs of foul play and ruled the manner “undetermined.” An autopsy said her death was caused by pancreatitis, electrolyte imbalance and chronic lead intoxication.

Stephen Beal later won $550,000 in a lawsuit against a life insurance company that denied his claim after asserting the death was not an accident.

In a statement on Monday, the Long Beach Police Department said detectives last year looked into the death of Christine Beal but could not find any evidence of foul play.