I get email and phone calls all the time "From" the FBI, the IRS, and the U.S. Marshall's Office telling me I have not paid my taxes or I've been otherwise behaving badly, there is a bench warrant for my arrest, and that I must pay the taxes and/or fines immediately or I will be carted off to jail. "Go to the nearest 7-11 and buy a Moneygram card in the amount of $$$$ and email the card number to our offices at..."
I'd be happy to help actual law enforcement in an investigation, but I'm afraid I will need some authentication. Like, I will look up the phone number of the law enforcement agency who sent the email in the Yellow Pages, and call that number. Number in the email/text/phone call? Yeah, right.
But first, that message would have to get past my "*sigh* yet another spammer/scammer" filter, which is, frankly, set at a high paranoia level.
If actual law enforcement starts doing this sort of thing regularly, the bad guys are going to join the party in a big way. Guaranteed.