Montgomery County detectives are investigating whether a workplace dispute over stolen merchandise led to the slaying inside a Bethesda yoga clothing shop, police said Saturday.

In court papers, detectives said the suspect’s coverup cracked under mounting forensic evidence and investigators’ questions.

Brittany Norwood, who was a standout soccer player in high school and college, is charged with murder in the March 11 death of her co-worker, Jayna Murray, 30. Norwood, 28, was being held at the Montgomery County jail Saturday without bond. She is due in court Monday.

Norwood at first portrayed herself as a victim in the attack, and police said she concocted the story that had downtown Bethesda on edge for a week: that two masked men entered Lululemon Athletica after closing time, sexually assaulted her and Murray, tried to steal money and left her tied up in the store, where she was discovered the next morning.

But according to the new court records, detectives slowly gathered evidence that contradicted the story. At one point in the court papers, Detective James Drewry labeled as “unbelievable” Norwood’s explanation of why she moved the victim’s car on a night that she supposedly spent tied up in a restroom.

From early in the case, detectives could see problems with Norwood’s story, according to the court filing.

At 8:12 a.m. March 12, a Lululemon employee arrived to open the store. She saw signs of disarray and heard “moaning coming from the back of the store,” according to the court filing. Police were called. Patrol officers who arrived took pictures of Norwood, who was lying on a floor in the restroom, her hands and feet bound with zip ties. She soon told detectives her story. Norwood said that while one of the masked men tried to steal money, the other assaulted Murray in the back of the store, according to the court papers. Norwood said she was then sexually assaulted.

But a medical examination of Norwood found no trauma consistent with the attack she had described, and further investigation showed that Murray had not been raped, according to authorities. In addition, remarking on Norwood’s injuries, Drewry noted that scratches running parallel across her chest, stomach and thighs had the hallmarks of self-inflicted wounds, according to court papers.

As doubts rose about details of her account, detectives studied photos of Norwood that were taken by the responding patrol officers. They concluded that the position of Norwood’s hands — above her head — indicated that she had posed herself, the papers say.

But it was evidence found in Murray’s car and the fact that the car had been moved that led to the complete unraveling of Norwood’s story, police said.

Detectives asked tough questions after trying not to push too hard in earlier interviews, police said. They asked if she moved the car, and she said she did, according to the court papers. They asked how that could be, in light of the rest of her story. Norwood said the two assailants let her leave the store to move the car but told her to come back in 10 minutes or they’d kill her, according to the court records. Norwood said that as she was moving the car, she saw a police officer but did not tell him what was going on.

Detectives will now focus on a motive. Norwood was a star soccer player at her high school outside Seattle and played the sport in college at Stony Brook University in New York. She appeared to encounter financial difficulties about three years ago, according to court papers and public records. But nothing in her past could explain charges that she stabbed and beat Murray to death.

Officials said Saturday that detectives are looking into whether the killing stemmed from Norwood “being suspected of stealing merchandise.” But detectives have not ruled out other possible motives.Kenny Fried, a spokesman for Lululemon, declined to comment about Norwood, saying the company didn’t want to interfere with the police investigation.

According to D.C. Superior Court records, Norwood’s landlord took action to have her and a roommate evicted from an apartment on Kenyon Street NW in Columbia Heights in 2008. A lien was filed against Norwood in 2007 for $19,953 by New York state’s higher-education agency.

It is unclear whether Norwood has retained an attorney. Online court records indicate that she had not. Efforts to reach relatives were unsuccessful. Several people who answered telephones listed to relatives politely declined to comment and hung up.

Norwood went to high school in Federal Way, Wash., about 20 miles from Seattle. At Decatur High School, she was a skilled soccer player and was named rookie of the year as a sophomore and most valuable player as a senior. Sue Ryan, head coach of the women’s soccer team at Stony Brook, said in a 2002 team release that Norwood had the mental makeup to be the best defender in the league.Brittany hates losing more than she likes winning,” Ryan said.

More recently, Norwood worked at the Willard InterContinental Hotel on Pennsylvania Avenue NW, according to a spokeswoman for the hotel. Barbara Bahny, director of public relations at the Willard, said, “Brittany was an employee but has not been at the Willard for some time.” Bahny said Norwood left the hotel about a year ago “on her own accord.”

Staff writers Maria Glod and Brigid Schulte and researcher Lucy Shackelford contributed to this report.