What to Know Pamela Butler was 47 when she vanished from her home in Northwest D.C. in February 2009.

Her ex-boyfriend, Jose Rodriguez-Cruz, was arrested Saturday and charged with her murder.

The acting D.C. police chief praised the cold case unit for making the arrest after eight long years.

Eight years after Pamela Butler disappeared without a trace, police sources say Butler's ex-boyfriend has been charged with killing her.

Jose Rodriguez-Cruz was taken into custody late Friday in Arlington, Virginia. He faces a first-degree murder charge and is due in court Monday.

The Environmental Protection Agency analyst was last seen Feb. 12, 2009, outside her home on Fourth Street in Northwest Washington, D.C. She was 47 when she disappeared.

Butler's family has spent every day waiting for closure.

"Wondering, not knowing every day. Is this going to be the day? This going to be the day? Never," said Thelma Butler, Pamela Butler's mother.

The family had Pamela Butler declared legally dead in August, after she had been missing for more than seven years. Derrick Butler, her brother, said her family wanted to settle her affairs and is accepting that she is gone.

The declaration allowed police to pursue murder charges when they made an arrest in the case.

Surveillance cameras at Butler's home captured video of Rodriguez-Cruz entering and exiting in the days following her disappearance.

It was not like Butler to vanish, her family said at the time. She had many routines and kept in close contact with her mother and sister.

On Saturday, family members said they always thought Rodriguez-Cruz was tied to Pamela Butler's disappearance.

"At least we know that we got the person that did it at this point. Doesn't make it any better for us, but it helps. And we know it's still a long road to go to finish this case, but we got there," Derrick Butler said.

Acting D.C. police chief Peter Newsham praised the cold case unit for the arrest.

"It was a fresh set of eyes on this case," Newsham said. "It is our belief this is a domestic violence case, but we can't get into it at this time."

D.C. Mayor Muriel Bowser said the Butler family's persistence and dedication also helped in the case.

"They have been focused on keeping Pamela's story in everybody's attention," Bowser said.

The chief said Rodriguez-Cruz waived extradition from Virginia and is in the custody of the Metropolitan Police Department.

He will be held until he appears in court to face the charges.