Pediatrician John Brickman Wall, 48, is accused in the petition of failing to properly care for the children, as well as inflicting "non-accidental harm, threatened harm and emotional damage."
But Pelle said during a recent interview with The Salt Lake Tribune that "the most immediate threat is a physical threat ... I thought maybe he would harm them, just like he harmed my mom and killed her."
The children the subject of a bitter custody battle since their parents divorced in 2006 began living exclusively with their father after their mother's death. Pelle moved out in January. The petition requests placing the other three children with another family or in protective custody.
Pelle said the last time he saw his mother alive, Wall had picked up him and his siblings from her house. When Uta tried to talk to Wall about the ongoing custody dispute, he just rolled the window up and drove away.
A year prior to his ex-wife's death, Wall told the children his life would be "better if he never saw Uta again," documents state.
The next day, Sept. 27, 2011, Uta's body was found by her boyfriend.
The medical examiner's office has not determined if her death was a homicide or suicide, but found the cause of death was drowning. Police have called her death suspicious.
Wall's criminal attorney, G. Fred Metos noted Tuesday that despite the son's allegations, no charges have been filed against Wall.
"You would think that if they had some evidence, it would have surfaced by now," Metos said.
Salt Lake City police continue investigating the case, but there have been "no significant changes at this point," said police spokesman Shawn Josephson on Tuesday. As for Pelle's petition, Josephson said, "That is a civil part of it, we continue our investigation on the criminal side of it."
Pelle said that on Sept. 27, Wall was acting strangely as the children who did not yet know their mother was dead got ready for school.
"His behavior that [day] was paranoid or freaked out," Pelle said.
Earlier that day, the two oldest children awoke to find their father absent and his car gone. That afternoon, Pelle saw a scratch across his father's eye and blood inside his eye, documents state. When Pelle asked about it, Wall said that Molly, the family's 4-year-old Labrador "became excited and accidentally scratched his eye" while he was sleeping on the porch the night before.
Wall also told Pelle there was a burrito stain on his car seat, so he took the car to get detailed early that morning. He also said he left the windows open to air the car out and someone stole his cell phone, according to court records.
The following day, Sept. 28, Salt Lake City police opened an investigation into Uta's death and questioned Wall, among several others.
A frightened Pelle slept with a knife and an airsoft gun under his pillow that night, not knowing why his dad was being questioned.
Wall told police he was asleep at his own home the night his ex-wife died, according to Pelle's court petition. Wall later came into Pelle's room with the other children trailing behind him as he cried and said, "Uta's dead and they think I did it," Pelle said.
Pelle recalls his dad sitting on the bed and breaking down emotionally. The youngest child consoled him by rubbing him on the back. Wall told the children not to go to school and leave him alone or he might jump to his death.
"But never did he deny killing her," Pelle said.
The final straw for Pelle, prior to moving out on his 18th birthday in January, came when his father asked what he knew about his mom's death and tried to give him a copy of the medical examiner's report.
"No, that is not how I want to remember my mom," Pelle told his dad. Wall then choked up and said, "I'm sorry," as he left the room.
Pelle said he no longer felt safe with his father. "That isn't a normal response to [my] statement," the teen said. "What is he apologizing for, if not killing her? That is when I decided to go."
Since the couple's divorce in 2006, Wall and Uta had been involved in a divisive legal battle over visitation and custody. Following her death, Wall has not allowed the children to communicate with their mother's side of the family, Pelle said.
"It has always been this alienation of my mom and her side of the family, even all of Germany, just because she was German," Pelle said.
Uta had tried to change the custody situation in court papers filed Sept. 21, 2011.
Six days later, late on Sept. 27, she was found dead by her boyfriend. A knife was in the tub beneath her body, and Xanax in her system, she did not have a prescription for the medicine, court documents state.
Bloody shoe prints were on the floor leading away from the bedroom, according to court records.
A medical examiner report states there was blood in Uta's bedroom, at the edge of the bathroom sink and on a window sill. The report also noted sharp force injuries to the woman's left wrist and left leg, "which are not typical of self-inflicted wounds seen in the setting of a suicide." The report said the wounds could be viewed as defensive injuries, if the woman had been struggling with an assailant.
Pelle later learned Wall had written a Xanax prescription for Pelle's grandmother, who lives in California. But the prescription was filled in Utah, and the grandmother never received the medication, Pelle said.
Wall, after speaking with police on Sept. 28, had asked his children, "Am I a monster? How am I supposed to know what I do when I'm asleep? What if I did it and don't remember?" according to the juvenile court petition.
He wanted his children to console him, Pelle said. "Even immediately after [her] death it was, 'What could you guys do for me?' " Pelle's said Wall said he felt his children should support him in his "trial of being accused for murder ... ."
Wall curled into a fetal position and rocked back and forth and cried, saying, "I want my mom," according to the petition.
One of the children called a neighbor asking for help, another child called Wall's parents in California.
Wall was taken to Utah Neuropsychiatric Institute, but no arrangements were made for the care or custody of the children, who were cared for by the parents of various friends.
When Wall's children visited him at UNI, he said he was concerned police would "do anything to convict" him, even "plant evidence. ... If they find my phone there, how can I refute that?" the petition states.
After Wall's release from UNI, Pelle said he didn't sleep well.
"I slept with my back to the wall every night … so that I wouldn't get stabbed in the back, I'd get stabbed in the front," said Pelle, adding: "... so I wouldn't be a coward and I'd be able to protect myself."
The three children remaining with Wall have been left without adequate food or transportation, the petition states. And when the children have asked about food, Wall stated, "Who is going to take care of ME?"
The children have resorted to hoarding food in their backpacks, and dog feces was found by a family friend "all over" the basement and basement steps, according to the petition.
Pelle notified Child Protective Services in March. But when no one ever contacted Pelle about doing anything, he filed his petition with the juvenile court.
Pelle said he hopes to see all the children in the care of new family. He also wants to see justice for what happened to his mother.
"I'd like to see him put away for his actions," Pelle said of his father. "They are unacceptable and they cannot be apologized for."