Update: What led to the arrest of David Watson

TUCSON, AZ (Tucson News Now) - ?

Pima County Sheriff's deputies arrested David Watson, 46, on Saturday evening at his home without incident, according to Chief Deputy Chris Nanos. He is charged with the murders of his ex-wife Linda Watson, her mother Marilyn Cox and Cox's friend Renee Farnsworth.

It took 15 years but the sheriff's office believes they have the right person. They say Watson has always been a prime suspect in the case.

The sheriff's office says it was not one particular thing that led to the arrest.

They say it's a combination of evidence and tips from the public put Watson behind bars. Finding Linda Watson remains back in 2011 played a role as well.

Chief Deputy Chris Nanos says it's hard to charge someone with murder without the body.

He also talked about the role technology played.

He says getting DNA results back isn't like what people see on TV, it takes time.

"As simple as it may seem to the mind that of course he did this, well you have to prove it its just not that simple," said Chief Deputy Nanos. "We need to do more work on the case and that took time and talking to people and finding information and tracking those leads down."

Watson is a captain at the Tucson Fire Department.

The Tucson Fire Department released the following statement Monday:

"The Tucson Fire Department is saddened to learn about the circumstances related to one of our employees. Our thoughts and prayers go out to the friends and family of the victims. David Watson was hired on the department in 1995 and has been serving in the role of captain since 2007. He is currently on an unpaid leave status."