The coward, who deleted his Twitter account after Noah's mum Fiona made the abuse public, operated the account under a fake name.
The account was accompanied by a profile picture of Diarmuid O'Sullivan - the 23-year-old Corkman, who alongside his father Tadg, shot 26-year-old brother Mark dead at their family home outside Castlemagner, Cork on October 25, 2020.
Diarmuid and Tadg subsequently took their own lives.
In a racist tweet, sent from the account and addressed to Fiona, the vile troll made a shocking and racist comment about her and her son Noah.
We have decided not to publish the offensive tweet.
But Fiona, who is campaigning for answers in relation to 14-year-old Noah's death last year, responded by reposting his Tweet alongside the comment: "I will not stand for evil trolls.
"How dare anyone think bullying anyone on social media is acceptable."
Teenager Noah's body was found naked in a storm drain in Belfast six days after he was reported missing back in June 2020.
An internal PSNI review has revealed that cops refused to pay overtime to officers who were assigned to search for him.
They cited "financial constrains" as well as "missing person fatigue" which has led to fears that this refusal could have delayed or hindered the PSNI's response.
Noah disappeared in June 2020 when he set off from his south Belfast home on a bicycle.
The young boy's disappearance sparked a huge search operation which involved hundreds of volunteers before his body was found in a storm drain six days later.
Last week, on behalf of Noah's mum Fiona, barrister Malachy McGowan referred to the internal review into the handling of the case during a preliminary hearing.
The devastated mum has alleged failings in how the cops investigated her son's disappearance and death.
McGowan has explained how Donohoe and her solicitor had held a "productive meeting" with the Police Ombudsman of Northern Ireland (PONI)about their investigation into the mum's complaint against the PSNI lodged in August.
He said: "Since the lodgement of that complaint, we have since received further disclosure some of which gives rise to further complaints, which should be investigated by PONI."
The latest developments come after an inquest into tragic teen Noah's death was delayed when Fiona's legal representative raised concerns about how much time was left to deal with outstanding issues in the case.
The coroner was told the family were concerned about having enough time to consider three expert reports which they received earlier this month.
And they were also waiting for results of an external review into the original PSNI investigation.
Donohoe's legal representative Brenda Campbell QC said: "It is no overstatement to say that this is one of the most sensitive, and in some respects the most controversial and mysterious inquests that this jurisdiction has encountered.
"Within the next eight weeks there is a huge amount of work to be undertaken, and it is just not feasible we will have completed."