Did Ex-Marine Impersonate Girlfriend to Hide Murder?

A retired Marine from Southern California who married another woman just weeks after the alleged murder of his girlfriend is now in custody, accused of the killing and its elaborate cover-up.

Investigators believe Brian Brimager, 43, disposed of Yvonne Baldelli's body, her small dog, and other belongings in November 2011 before tricking her family into believing she was still alive with phony emails and withdrawals from her bank account.

Brimager was arrested Thursday north of San Diego after being indicted by a federal grand jury on charges of obstruction of justice and making false statements.

According to the unsealed indictment, Brimager, 37, and Baldelli moved together to the small island of Isla Carenero in Panama in September 2011. Prosecutors say within a month Brimager was sending emails to another girlfriend referred to as "K.W." discussing moving back to California to live with her and their young daughter.

The indictment alleges Brimager soon began fighting with Baldelli, leaving her with bruises around her eyes and on her arms. The couple was last seen together at a restaurant November 26, 2011. Investigators believe he killed Baldelli that night; the next morning used her laptop computer to search for information on how to remove blood from a mattress.

Baldelli's body has never been found, but the indictment suggests some of her belongings were recovered. Prosecutors say Baldelli "disposed of physical evidence of his crime, including putting personal items belonging to Baldelli in approximately 10 large trash bags." The bags containing her clothing, make-up, and jewelry were left on a dock for disposal near the hostel where the couple were living, according to the indictment.

"Brimager engaged in a pattern of conduct designed to corruptly obstruct, influence and impede investigation into her disappearance," the indictment alleges.

Prosecutors say on November 29 Brimager began using Badelli's email account to send messages to friends and family stating she was leaving the small Panamanian island to move to Costa Rica with another man. They say Brimager made a stop-over in Costa Rica on his way back to California to withdraw $200 from her bank account to make it appear she was there.

According to the indictment, Brimager's other girlfriend "K.W." picked him up at the airport in San Diego on December 12, 2011. "He proposed to her two days later and they married shortly thereafter," said prosecutors in the indictment.

Brimager is schedule to return to U.S. District Court for a detention hearing on Friday at which prosecutors will ask that bail be denied. Badelli's family released a statement Thursday on a Facebook page dedicated to finding her.

"We sorely miss Yvonne's melodious laugh, contagious smile, and her kind heart," said the statement. "Yvonne did not deserve to be ripped from our family. We will never recover from her absence. We are confident in the U.S. government's case against Brimager."

A call to a lawyer for Brimager wasn't returned.

More ABC News