PARKLAND, Wash. -- Sheriff's deputies have arrested an active-duty soldier who they say fatally shot a man and woman and kidnapped the couple's young child.

Sheriff spokesman Ed Troyer said the 8-month-old girl was recovered safely and is being cared for by Child Protective Services.

The two victims were found shot to death in a home Sunday evening in the 700 block of 110th Street South. Their names have not been released, but both are in their 20s and are active-duty soldiers based at Fort Lewis.

The two are believed to have been killed on Saturday.

The woman who was arrested is also a soldier, but her relationship to the man and woman who were killed was not immediately known, and investigators were trying to determine what prompted the killings.

The 22-year-old was being questioned by detectives and was expected to be booked into the Pierce County Jail. Troyer said she was arrested at Fort Lewis and had the victims' baby with her at the time.

"Hopefully as we do our investigation throughout the night we'll determine what led up to this," he said. "At this point we don't have a motive."

Troyer said deputies will be working with military police to serve search warrants at the Army base and interview friends and neighbors of the victims and the suspected shooter.