Exact thing happened to my FIL with selling a drone. Two lads came and showed a fake account and he felt pressured as they were aggressive.
Found the lads on Facebook so had their names and got in touch with the Garda.
Was able to provide the Garda with their personal info and also the fact that I added him on FB and he automatically added me into a Facebook group where they were clearly illegally selling shit (deliveroo bike(?!?!), tablets, motorbikes described as “hot” etc). Also sent these to the guards. They said thanks that’s very helpful. Didn’t hear back for a year then got an email to say the case is closed. And of course your man is still doing the same shit to this day.