Police in Arizona may be one step closer to solving a 15-year-old cold case murder of a Tucson mother and the subsequent related slayings of her mother and neighbor. David Duane Watson, a 46-year-old Tucson firefighter, was arrested without incident Saturday on charges he killed his ex-wife Linda Watson, 35, in what detectives say motivated by a custody dispute over their daughter. Police say the dispute continued after Watson's murder as her mother Marilyn Cox, 63, tried to obtain visitation rights. Three years after her daughter went missing, Cox and her neighbor Renee Farnsworth, 53, were shot dead in the driveway of Linda Watson's home. Tragic: Police say Linda Watson, left, was killed by her ex-husband David Watson during a 2000 custody dispute over their daughter Jordynn, right. Three years later, they say Mr. Watson murdered Linda's mother Marilyn Cox, center, as she tried to gain visitation rights over the girl in 2003 . Cold case closed? Seen here upon his arrest late Saturday, David Watson has been charged in the murder of his ex-wife, ex mother-in-law and an innocent neighbor . Police said at a press conference on Saturday that Mr. Watson had been the prime suspect in the murders from the start, reports the Arizona Daily Star. Watson has been charged in all three homicides, with police cited DNA evidence. Chief Deputy Chris Nanos said sheriffs never gave up on the cases, writes Tucson News Now. 'It just goes to show you that the men and women of this department are bulldogs,' said Nanos. 'We'll keep tracking you, we'll find you and you will get punished for the crimes you do.' Linda Watson was reported missing in August 2000 after she failed to pick up her daughter from the home of David Watson. She was last seen by a friend who'd dropped her off following a church function. Inside the home were found Ms. Watson's pager, Bible and purse. The door to her home was found open and her blood was discovered at the scene. Linda Watson was reported missing in August 2000 after she failed to pick up her daughter from the home of David Watson. She was last seen by a friend who dropped her off at her Tucson home after church. Her body would not be found until 2012 . Police say David Watson had been the primary suspect since 2000, but have only now tied him to the crime with what a Sheriff's Department official said Saturday was 'DNA evidence' After her disappearance, Marilyn Cox, became intent on finding her daughter and devoted her life to the search. She--along with the girl's paternal grandfather--was granted visitation rights for her granddaughter. However, Cox said at the time that Watson obstructed those rights, so she petitioned for a review. In May 2003, with another custody battle heating up, Cox was shot dead in a drive-by shooting in the driveway of the home from which her daughter had disappeared years before. Her neighbor, Renee Farnsworth, was also killed in the shooting. Meanwhile. Linda would not officially be declared dead until 2006. Her body wouldn't be found until six years after that when remains discovered in the Arizona desert turned out to be hers. Watson was scheduled to be arraigned Sunday morning at Pima County jail where the Sheriff's Department would recommend a $ million bond, reports KGUN. Marilyn Cox (right) was fighting to exercise her visitation rights over Jordynn Watson when she and her neighbor Renee Farnsworth were gunned down in a 2003 drive-by shooting outside the very home from which Linda had disappeared three years earlier .
Pima County Sheriffs say David Watson, 46, killed his ex Linda Watson while they fought over custody of their daughter in 2000 .
Three years later, police say Watson murdered his ex mother-in-law in a drive-by shooting at the very home where Linda Watson first vanished .
Marilyn Cox had been fighting for visitation rights over her granddaughter - she was gunned down alongside her neighbor Renee Farnsworth in 2003 .