Answer for Question
I assume you’ve read this article of mine: FBI “Ransomware” Phishing Scam Affects Mac Users – How To Bypass
Bottom line, these are scams as the FBI does not contact you through a web site. If they wanted to “bust” you, they’d show up at your door.
Just close the window and don’t worry about it. It is an extremely common scam. You may see it again in the future.