She did not want to share him with his 3-year-old from a previous relationship; he worried she would leave him.
The roiling emotions proved deadly for little Brendan Link Creato, a Camden County prosecutor told a judge Tuesday, seeking high bail for the boy's father, who had reported him missing and now is charged with his murder.
Weeks before Brendan's pajama-clad body was found in Haddon Township woods, David "D.J." Creato Jr. was distraught and arguing with his 17-year-old girlfriend to keep her from leaving him, Assistant Prosecutor Christine Shah said.
The girlfriend, a juvenile whom Shah did not name but who has been identified as Julia Spensky, had warned Creato she disliked children and resented his devotion to the boy. Shah said authorities learned of the fraught relationship mostly from the couple's numerous text messages and online postings.
"She issued an ultimatum to him," Shah said Tuesday after Creato, charged with the Oct. 13 murder of his son, was brought into a Camden courtroom for his first appearance.
Shah said medical examiners determined the boy died of "homicidal violence." Superior Court Judge Edward McBride set bail at $750,000 - lower than the $1 million sought by Shah, but higher than the $250,000 a defense attorney said might be appropriate.
Creato, 22, did not confess to police, but Shah said he told investigators that he was feeling "jealous and anxious" in the hours before he noticed his son had disappeared from his apartment, and that he had been worried that the woman he loved had found someone else.
Creato called 911 at 6:07 a.m. Oct. 13 and told the dispatcher that his child must have unlocked the door and wandered off, Shah said.
"I just woke up, and my 3-year-old's missing," Creato said, according to a recording of the call. "I just woke up and he wasn't in my apartment. I don't know if he wandered out or what happened. I don't know where he is. The door was locked. I guess he unlocked it and left."
Shah said his voice during the call had a "flat affect and tone."
Brendan had been "very afraid of the dark," Shah said, to the point that he had been reluctant to go to the bathroom at night, according to interviews with grandparents and other relatives who had babysat him.
The stretch - about three-quarters of a mile - between Creato's apartment and the muddy spot by the Cooper River where Brendan's body was found is extremely dark at night, very steep at one point, and difficult to negotiate, she said.
Besides, Shah said, Creato was sleeping less than nine feet from the door and would have awakened if Brendan had unlocked it or if an intruder had entered.
It is "a circumstantial case" in which the "circumstances are quite compelling," Shah said, laying out a chilling narrative.
Much of D.J. Creato's life was online, she said. Investigators examined 9,487 text messages he exchanged with his girlfriend after meeting her in June on Tinder, a dating website, and during an "intense romantic relationship" that continued into October. Shah said the teen had written a series of "unbelievable" blogs in which she described her "strong dislike of children."
Creato, shackled and wearing blue jail garb, said nothing during the hearing and mostly looked down.
His attorney, Richard Fuschino Jr., said the prosecutor's version of what happened was improbable, and that his client had cooperated fully and truthfully with investigators.
"He spent an entire day answering the questions of investigators," Fuschino said.
Shah, in saying Brendan died of "homicidal violence," said an examination of his brain showed an abnormality consistent with oxygen deprivation that can be caused by asphyxiation, drowning, or manual strangulation.
The prosecutor said there was unhealed bruising to the right clavicle, near the neck, which indicated that the toddler was injured prior to his death. There was no evidence that an accidental injury or disease caused the child's death, she said.
Shah did not say where the murder took place, but disputed Creato's suggestion that Brendan had gone missing. "Never once had he left the apartment or his mother's house or his grandparents' by himself," she said.
Shah said that on the night Brendan was killed, Creato had called his girlfriend eight times, and that he noticed from her Snapchat online account that she had met up with a "guy he was jealous of." Then, at 1:37 a.m., he checked his phone again, though he told investigators he had gone to bed at 10 p.m., Shah said.
Shah said problems developed between Creato and his girlfriend after she began attending college in New York and could only visit him on weekends. The teen, who previously lived in Pennsylvania, told Creato that he would have to give up taking custody of Brendan every other weekend to be with her, Shah said.
McBride, the judge, said that if Creato posts bail, he will not be allowed to leave the state or make any contact with Brendan's mother, Samantha Denoto, or her family.
Denoto sat stoically in the front row of the packed, hushed courtroom and declined to comment afterward. She and Creato, who were not married, had shared custody of Brendan. She has made no public comment since the boy's death, when her family issued a statement saying it was "heartbroken" and wanted privacy.
The only sign of emotion Denoto showed was when Shah told the judge that Creato and Spensky still were communicating. Denoto shook her head vigorously, as if she did not believe that was possible.
Shah said the teen was away at college when the child was killed.
In an interview in November, Fuschino identified Creato's girlfriend as Spensky and said she had been at Creato's apartment the weekend before Brendan's death.
In a Tumblr post after Brendan's body was discovered by a K-9 unit, Spensky wrote that she was "possibly a suspect in a homicide investigation."
The post, subsequently removed, also said: "I was advised by my attorney not to speak to anyone about my case. . . . My boyfriend is in worse trouble than I am and can't leave the state he's in."
Spensky's attorney, Joseph Sorrentino of New York, said Tuesday that he had no comment.
Shah said that while they dated, Creato and his girlfriend had visited the spot where Brendan's body was found about 30 times. The pair had taken pictures there and posted them online.
Creato told investigators that it was a "favorite place . . . and he referred to it as spiritual to him," Shah said.
Brendan "was placed there," Shah said, noting that the socks he was wearing when his body was found had no dirt on them.
If convicted of murder, Creato would face a minimum of 30 years in prison without parole and a maximum term of life imprisonment with at least 67 years without parole, the judge said.
Dan Keashen, a spokesman for the county jail, said Creato was being held "in the special management unit under close observation."
In requesting bail of $1 million, Shah said Creato had "violated a most sacred trust, a trust between a parent and a child."
The judge said that bail in New Jersey is based on the risk that a suspect will flee, and he said Creato had no criminal record and had not attempted to disappear during months of investigation. "The defendant has been involved in the investigation since the outset. He has always been available," McBride said.
The judge said $750,000 was proper because of the seriousness of the crime.
Staff writer Michael Boren contributed to this article.