The assailants who killed one yoga store employee and assaulted another in Bethesda likely followed them into the store and beat them, Montgomery County’s police chief said Monday during a news conference at which officials also announced a reward of $136,000.

Chief J. Thomas Manger also provided a more exact time line of the slaying:

At 9 p.m. Friday, the two workers closed the store, Lululemon Athletica, along Bethesda Row. At 9:45 p.m., they set the alarm and left the store. A short time later, one of them realized she had left something behind, called her coworker, and the two met back at the store. They entered about 10:05 p.m., Manger said.

The two men, wearing dark clothing, gloves and masks, followed “seconds” behind them, Manger said.

Both women -- 27 and 30 -- were sexually assaulted and beaten, Manger said. One was beaten to death, he said. The second survived, and was discovered the next morning.

Before the news conference, police had declined to say how Jayna T. Murray, of Arlington, was killed. But law enforcement sources confirmed a horrific, bloody scene inside the store.

Because the men were covered up, police have only come up with faint descriptions: One 6-feet tall, the other 5-feet-3-inches tall.

Manger said that at this point in the investigation, the case appears to be a random crime of opportunity. Law enforcement sources confirm that nothing has surfaced so far to indicate anything else.

Capt. Paul Starks, a police spokesman, said the survivor continues to improve.

The company, Lululemon Athletica, has donated $125,000 into a reward fund, police said. Federal Realty also is offering $10,000. Crime Solvers is offering $1,000. The money is for information “that leads to the arrest and/or indictment of the persons responsible for these felony crimes,” police said.

The numbers to call are 240-773-5070 or 240-773-TIPS.

[This post has been updated.]