(I feel so sorry for this kid) Internet Fraud against developmentally delayed person

I know this really nice kid that happens to be disabled. I just found out he's being taken by some online dating scam and I really want to do something about it.
The person taking advantage of him claims to be a girl but it's probably a guy so I will refer to this person as "IT"

It's already scammed him for over $4000.00.... I have the "IT's" telephone number and have text it and told it that we know what's going on and demanded IT STOP! But IT continues to text him and tell him we're harassing it. So now the disabled kid is pissed at us.

IT convinced him IT was on it's way to see him and needed money to get there, IT also scammed money for money for school etc... Ehhhh, how can we stop it?