Four years after an explosion at a day spa in Aliso Viejo killed one woman and injured two others, the fate of a Long Beach man accused of creating and placing the deadly home-made bomb that blew up the business will soon be in the hands of a Los Angeles jury.

A more than two-month trial at the federal courthouse in Downtown Los Angeles wound down Thursday, leaving jurors tasked with deciding whether defendant Stephen Beal was an obsessively infatuated man who decided to kill his ex-girlfriend, as prosecutors allege, or if he is the innocent victim of a quick rush to judgement by law enforcement, as defense attorneys countered.

Beal is accused of crafting an explosive devise in a cardboard box that detonated on May 15, 2018 when it was opened by 48-year-old Ildiko Krajnyak. The blast also injured two of Krajnyak’s clients and blew through the spa building, showering neighboring offices with glass and debris.

Assistant U.S. Attorney Mark Takla told jurors during closing arguments Thursday that a rage-filled Beal wanted to both “obliterate” Krajnyak and destroy her business.

“He blew her up,” Takla said. “He made a bomb, he dropped it off and he walked away … he decided if he couldn’t be with her no one could.”

Craig Harbaugh, one of Beal’s attorneys, told jurors that Beal had no reason to kill Krajnyak and accused investigators of ignoring other potential suspects and focusing solely on Beal.

“They concluded because Mr. Beal could have built a bomb, Mr. Beal must have built a bomb,” Harbaugh said. “Their entire investigation was analyzed through the lens that Mr. Beal must be guilty.”

Beal — a co-owner of the spa who had begun dating Krajnyak in 2016 after the pair met online — quickly became the focus of the ensuing investigation after contacting law enforcement hours after the fatal blast. An FBI search of Beal’s Long Beach home allegedly turned up 130 pounds of “explosive precursors” that Beal contended was used for his model rocket hobby.

Investigators also learned from friends of Krajnyak’s that Beal was “freaking her out” by constantly monitoring her and trying to control her life, according to prosecutors.

Beal was one of a small group of people with keys to the spa suite, prosecutors noted, and surveillance footage showed Beal’s Prius entering a parking lot a block away from the spa four days before the explosion, while Krajnyak was on a trip to Hungary with a potential romantic partner.

Serial numbers from a chunk of the battery that investigators believe served as the power source for the bomb were tracked to a shipment of batteries to CVS stores in Southern California in March 2018. Prosecutors say receipts and surveillance footage showed Beal purchasing such a battery, along with a box that one of the women who survived the explosion identified as looking similar to the box that held the bomb.

Beal’s attorneys noted that he cooperated fully with the investigation, agreeing to talk to law enforcement at length, letting them search his home, and telling them about his rocket-building hobby and his romantic and business ties to Krajnyak.

“That isn’t a criminal mastermind,” Harbaugh said. “That is an innocent man with nothing to hide.”

Harbaugh also noted other potential suspects he contended law enforcement didn’t investigate fully. They included an electrician working as a maintenance man who had keys to the spa suite and a married former lover of Krajnyak’s, who had military experience and whose wife had previously attacked Krajnyak over the affair.

Prosecutors said of the people involved in the investigation, only Beal had the knowledge to construct such a bomb.

“The bomb was the defendant’s fingerprint,” Takla said. “The bomb was the defendant’s DNA. The bomb was the defendant’s signature.”

Jurors are expected to begin their deliberations on Monday morning. If convicted, Beal could face a potential life sentence without the possibility of parole.