A PSNI investigation is under way after a video appeared online showing one man accusing another of being a paedophile and ordering him to leave a play park.
However, some people who saw the footage and claim to know the man being challenged have said he has mental difficulties.
Some also said he has no convictions for being a paedophile and didn't understand what he was being asked.
The original poster was himself accused of being a bully who had made a vulnerable person even more pregnable.
The film posted on social media over the weekend shows the moment the man is confronted while sitting alone on a park bench. It's understood the video - which is almost two minutes long - was recorded in a public park in Belfast on Sunday.
The video has been shared on social media sites including Twitter and Facebook with the man's identity clearly visible to viewers.
One man challenges the alleged 'paedophile' over why he is in an area where families and children are known to visit.
The video begins with the man asking the other whether he is "allowed near children".
He replies: "I'm not near anybody.
"I'm just sitting here minding my own business."
Again, he is asked if he is allowed near children and this time he replies: "No."
After being told he is not allowed in the park he starts to leave the area.
The man behind the camera is then heard saying: "You see the next time I see you in this park, there will be trouble. Do you understand? You're a paedophile. You have been convicted of paedophilia, is that correct?"
"Yes," the other man replies.
The original footage, which was taken down hours after it appeared online, has been shared dozens of times.
While the area where the video was taken appears to be empty, a number of people including a child can be seen entering the park at the end of the recording.
At this point the alleged "abuser" is taped leaving the vicinity while the cameraman continues to threaten him. He warns the man to "stay out" of the area and orders him to move out of the Northern Ireland town.
"You know you are a convicted paedophile, so take yourself out of this park immediately.
"Take yourself off."
While some people congratulated the man issuing the challenge, others strongly disputed the accusation that the other man is a paedophile - saying instead he has a learning difficulty.
"Next time don't try and play the hero - phone the cops!" wrote one person.
A spokesman for the PSNI said: "Police are aware of a video posted on social media in which a male is challenged by a man in a local park. Enquiries into the matter are currently ongoing and there are no further details at present."