WASHINGTON - It's a crime that had already captivated the D.C. region: an employee of a Canadian yoga apparel store in a well-heeled Maryland suburb, one of the safest in the area, apparently raped and murdered by two masked thugs inside the shop.

But the latest developments are even more stunning -- Jayna Murray's 27-year-old female co-worker has been charged with first-degree murder in the slaying a week after telling police that the two men entered the Bethesda Lululemon Athletica shop, one of hundreds in the Vancouver-based chain, and proceeded to terrorize them.

Murray died from her wounds in the March 11 attack, while Brittany Norwood told police she was spared.

The 30-year-old Murray, in fact, suffered "catastrophic" injuries so heinous that they upset some of the police on the scene. Norwood, a onetime high-school soccer star from Washington state, was found bound and bruised near Murray's body in the back of the store the next day by a co-worker reporting for work.

Police say they charged Norwood after her story began to seriously unravel.

"When the investigation began, detectives had only the story of Ms. Norwood to go by," J. Thomas Manger, chief of police for Maryland's Montgomery County, told a news conference.

But he added "the forensic evidence and the physical evidence was not supporting what Ms. Norwood had told us."

Norwood had told police that the women had locked up the store for the night, and when she realized she'd forgotten her wallet inside, she called Murray and asked her to come back. An hour later, both women returned to the store.

While police say Norwood's timeline matches other evidence they've gathered, little else does.

Local television stations broke into regular programming on Friday night to broadcast images of Norwood, 27, slender and fit in Lululemon garb, being taken into custody in nearby Rockville, MD. The events unfolded the day before Murray was to be laid to rest in Texas, where her parents reside.

Manger said there was no evidence either woman was raped that night. And while Murray's wounds were horrific -- an autopsy determined she'd been stabbed and beaten -- Norwood's were merely superficial, leading police to suspect she inflicted them herself and tied herself up.

Police also say witnesses at the nearby Apple store, in a high-end shopping area known as Bethesda Row, reported hearing two women arguing loudly that Friday night inside the Lululemon shop. And they say only two sets of bloody footprints were found in the store; one belonged to Norwood, and another to a size 14 shoe used in the shop by customers.

They also reportedly found physical and forensic evidence in Murray's car that lead them to Norwood. For reasons apparently unknown to investigators, the suspect allegedly moved the car, originally parked in front of the store, about three blocks away.

The investigation is still active, and it wasn't clear whether someone else was in the store with Norwood and Murray, although police sources told the Washington Post they don't believe anyone else was involved in the crime.

Little is known about the relationship between Murray, who lived in nearby Arlington, Va., and Norwood, and whether they had any problems as co-workers.

Reports suggested the only hint of a past brush with authorities by Norwood involved her failure to pay rent at her D.C. apartment. She was then evicted.

A YouTube video of the blond, smiling Murray bungee-jumping on her 30th birthday has received thousands of hits since her death. A co-worker has described her as "spunky" with a joy for life.

Candle-lit vigils were held in honour of Murray, not just in Bethesda but outside Lululemon stores in New York and other cities, even after news of Norwood's arrest.

The events had frightened residents and retailers in downtown Bethesda, with some reporting business had dropped off in the days following the attack due to fears that two murderous male culprits were on the loose in the area. Some shopkeepers moved to install surveillance equipment and beef up other security measures.

The Lululemon store is closed indefinitely. The company issued a statement about the arrest.

"We are grateful for the dedicated members of the law enforcement community who have been working diligently to solve this crime and apprehend those responsible," the statement said.

"Our first priority remains with the families and team members affected by this horrible tragedy and supporting them through the next stage of the recent developments."