A Salt Lake City pediatrician was arrested and charged with murder Thursday - 18 months after the body of his ex-wife was found in an overflowing bathtub. John Brickman Wall, 49, was charged in the death of Uta Von Schwedler, also 49, a biologist at the University of Utah. Police called the death suspicious after it occurred in September 2011, and the couple's oldest son fueled speculation by saying he believed his father did it. Von Schwedler's family and friends had become increasingly worried that the investigation had hit a dead end. But they welcomed the news of the arrest and thanked police. "The arrest of John Wall for the murder of Uta von Schwedler is a long-awaited moment for those who loved Uta in their quest for justice," said Margaret Olson, an attorney for Pelle Wall, the 19-year-old son of Von Schwedler and John Wall. Salt Lake County District Attorney Sim Gill said there wasn't a single piece of evidence that broke the case open. Instead, he said, a combination of factors stacked up, allowing prosecutors to finally charge the doctor. Some of the key pieces included DNA evidence under the victim's fingernails that didn't rule out Wall; the fact that von Schwedler died in part due to an overdose of Xanax but didn't have a prescription and was not depressed; and Wall's inability to explain his whereabouts the night of her death. "It was a multiple set of facts that came together to create the mosaic that allowed us to cross that threshold to press these charges," Gill said. Wall was being held on $1.5 million bail, with his first court appearance expected Tuesday. He was also charged with aggravated burglary. His attorney, G. Fred Metos, said Wall maintains his innocence. Charging documents indicate police interviewed about 30 people while investigating the killing. They found blood stains and overturned objects in the victim's bedroom. The back door had been unlocked, prosecutors say, and a key was missing from its hiding place. She had cuts on her wrist and leg, but the medical examiner determined she died from drowning and a fatal amount of Xanax, the documents show. In addition, a family friend told police John Wall was driving in the area at about 7 a.m. on the day of the killing. Authorities also noted that John Wall had written his mother a prescription for 30 Xanax tablets in May 2011 and filled the prescription himself. Following an interview with police, the documents state, John Wall told a friend, "Only a monster would do what was done to Uta. If it was me, I don't remember. The couple married in 1990 in California and moved to Salt Lake City in 1994. Von Schwedler grew up in West Germany, the oldest of four children. Friends say she loved to run, bike, hike and spend time with her children. After the couple divorced in 2006, they become ensnarled in a bitter custody battle. Pelle Wall, the oldest of their four children, testified at a custody hearing that he was so afraid of his father when he was living with him that he slept with a pellet gun and a knife. Police say John Wall told people that his ex-wife was ruining the good things in his life and blamed her for his problems. The couple's other children are 17, 14 and 12. John Wall never lost custody of the two youngest, though they were temporarily placed in another home after Pelle Wall petitioned the court to remove them from his father's house, said Rebecca Skordas, an attorney serving as a spokeswoman for the family. Now that John Wall is in jail, arrangements are being made to place the two youngest children with family members. The 17-year-old is an emancipated minor who has already moved out, she said. Follow Brady McCombs at https://twitter.com/BradyMcCombs.