Linda Watson vanished on Aug. 20, 2000. The next morning, a repairman stopped by her house on a sandy stretch of road in Tucson and found the back door open. A cup lay smashed on the floor near the entryway, but there was no trace of the single mother, save for a few drops of her blood hidden underneath a garbage bag.

Marilyn Cox plastered posters around town promising a reward for information about her daughter’s disappearance. As the months dragged on, she appeared on local radio programs pleading for help catching her daughter’s abductor. “She’s my only daughter,” Cox said, weeping into the studio microphone. “She’s my baby.”

But instead of solving her daughter’s case, Cox became part of it. On May 7, 2003, Cox and a neighbor were gunned down in the driveway to her daughter’s home, where Cox had been living since Linda’s disappearance.

A few months later, Linda’s corpse was found in the desert mountains west of the city.

If the murder of mother and daughter in the same spot wasn’t enough of a coincidence, both women were involved in legal battles with the same man when they died: David Dwayne Watson, Linda’s ex-husband.

For 15 years, David Watson was the main suspect in the slayings. But it wasn’t until Saturday that the Pima County Sheriff’s Department finally arrested the firefighter.

The arrest may provide closure in the cold case. Yet it also raises uncomfortable questions for local authorities. Why didn’t they arrest David Watson sooner? Could they have saved Marilyn Cox and her neighbor if they had taken the mother’s suspicions more seriously? How could they let an allegedly homicidal firefighter act the hero, advancing to be a captain?

So far, the sheriff is staying quiet.

“People have been asking how we broke the case,” Deputy Tracy Suitt told The Washington Post. “Basically, just a lot of hard work. Everything we came through we investigated it to the fullest. That’s where we are right now. A lot of the information we can’t talk about right now because it would be detrimental to our case.”

Suitt said his department is worried that releasing more details on the breakthrough might backfire.

“If for some reason this man is released, we don’t want him to be able to guess the identities of our witnesses from the information we’ve released,” he said. “We are holding onto everything to protect our witnesses.”

Suitt said it could be weeks before authorities reveal why, exactly, they are charging David Watson with the three murders now, almost 12 years after Cox and a neighbor were killed and nearly 15 years after Linda Watson’s disappearance. The Sheriff’s deputy said David Watson has worked for the Tucson Fire Department since 1995 and was promoted in 2007 to captain. According to the Associated Press, however, the fire department was not notified that David Watson was a suspect in the murders.

“We can’t just call them up and say this person is a suspect in homicide until we have enough evidence. That would be irresponsible,” Suitt said. David Watson is on unpaid leave, according to the fire department.

“The Tucson Fire Department is saddened to learn about the circumstances related to one of our employees,” fire department spokesman Barrett Baker said. “Our thoughts and prayers go out to the friends and family of the victims.”

Authorities admit that suspicion has always centered on David Watson, who was locked in a bitter custody battle with his ex-wife when she disappeared. Three years later, Cox was also fighting David Watson for custody of her granddaughter when she was gunned down.

Chief Deputy Chris Nanos praised the department for not giving up on the case. “It just goes to show you that the men and women of this department are bulldogs,” Nanos said. “We’ll keep tracking you, we’ll find you and you will get punished for the crimes you do.”

The Cox family has also insisted all along that David Watson was involved in the murders. On Saturday, Marilyn Cox’s sister, Pat Hinkle, released a statement expressing “shock” and “joy” over the long-awaited arrest, but also a hint of frustration that the arrest took so long when all the clues seemed to be there from the beginning.

“Our family is overjoyed that David finally is behind bars. We’ve waited for 15 years for this justice, but it is also bittersweet,” Hinkle said. “He is still destroying lives; his children are going to have to live with this for the rest of their lives. We are all still in a kind of shock; after so many years we sometimes felt it would never happen.”

Here is a timeline of the tragedy:

  • Aug. 20, 2000: Linda Watson is last seen by her mother. The two attended church and ate lunch together before Marilyn Cox dropped her daughter off at her home.
  • Aug. 21, 2000: A repairman finds Linda Watson’s backdoor unlocked. Inside the house there are signs of a struggle, including a broken cup and drops of blood.
  • Aug. 21, 2000: Linda Watson misses an appointment with her attorney to file a restraining order against David Watson.
  • Aug. 23, 2000: Linda Watson never shows up to pick up her daughter from David Watson.
  • Aug. 24, 2000: Linda Watson misses a custody hearing.
  • 2000 – 2003: Marilyn Cox appears on local media to plead for help in solving her daughter’s disappearance.
  • May 7, 2003: Cox and her next-door neighbor, ReNee Farnsworth, are shot after going shopping.
  • Oct. 2003: Linda Watson’s body is discovered in the desert to the west of Tucson, along with the bodies of undocumented immigrants. However, the corpse is too decomposed to be identified.
  • 2011: Authorities finally identify the body found in the desert as Linda Watson’s.
  • April 25, 2015: Sheriff’s deputies arrest David Watson. Prosecutors charge him with the murders of Linda Watson, Marilyn Cox and ReNee Farnsworth.