In September, the 17-year-old boy pleaded guilty to harassing BBC News Northern Ireland's Aileen Moynagh between October 25, 2020, until the end of February last year.
The boy, who has a range of complex disorders and cannot be identified because he is a minor, stalked her online after developing an "obsessive crush".
The teen had been previously cautioned about similar trolling of two female RTE staffers and had an "unhealthy interest" in women journalists.
After a one-month adjournment, the case resumed at the Dublin Children's Court. He entered an additional guilty plea to threatening to harm another broadcast journalist, who was not named during the proceedings.
He made the threat on November 9 last to a Garda and two other people at a youth justice project, intending them to believe he would cause her serious harm.
The court heard the teenager confessed to previously hiding in bushes on the grounds of her workplace in Dublin and that he watched her drive out of a car park.
Detective Garda Michael McCallion said the boy threatened that he had wanted to disfigure her.
Defence solicitor Eoghan O'Sullivan described it as an escalation of the teen's behaviour. He had believed injuring the woman would help him cope with his obsession because she would not be able to work.
Mr O'Sullivan outlined how child mental health services diagnosed that it was not a mental health issue, and the boy's case was referred to disability services.
The latest journalist he targeted did not give a statement and was not required to attend the court proceedings.
Questioned by the solicitor, an HSE official conceded the teenager needed a residential therapeutic placement.
They identified an appropriate facility, however, budget issues prevented it from being available.
So instead, they offered "wraparound services", including cognitive behaviour therapy, in the community.
HSE officials told the court they were unaware of the court proceedings until reports appeared in the news media.
The teen's father vented his frustration at a lack of multi-disciplinary help for his son.
Addressing the court, he told Judge Paul Kelly he pleaded with mental health services for years, but the level of support received was inadequate. He described the developments as a "self-fulfilling prophesy".
He told the court a behavioural analyst had also felt that the services offered to his son were insufficient.
"They have been talking about it for six years, and nothing has changed," he said, adding, "I'm sorry for my tone".
The case resumes later this month when updated welfare reports will be furnished to the court.
The youth remains on bail with conditions restricting his movements and internet access.
Earlier, Detective Garda Ken McGreevy outlined a litany of unsolicited and unwanted communications from the boy, then aged 16, to the BBC journalist. He sent them via email, Twitter, Facebook and LinkedIn.
At one point, the boy travelled to Belfast despite being warned by gardai not to contact her, and he went to within a couple of hundred yards of her workplace.
Out of fear, she moved out of her house for five days.
She reported it to the PSNI, but the complaint was not passed on to the Republic, and the journalist later contacted the gardai.
The "high functioning" boy, who wants to be a journalist, had been barred from Twitter 150 times under various aliases.
Last month, in a victim impact statement, Ms Moynagh told the court she hoped the case would "shine a light" on the dangers of social media and act as a deterrent.
Concerns were raised at an earlier stage that the boy had also been sending unwanted messages to a female student in Galway.
He also caused a person to lose their job after he made an unfounded, false allegation against them, the court was told.
The teen had a breakdown and was hospitalised for two months after similar harassment of two RTE journalists, which did not result in a court prosecution.