It sounds to me like you got the "FBI Child Pornography Ransomware" virus. I deal with it all the time. It's a tough nut to crack, requiring a reboot into Safe Mode with Command Prompt. It's nothing that you did personally; viruses like these sniff you out, determine vulnerability, and then indiscriminately zap you. The best program to get rid of this stuff is Malwarebytes. It's free, and it works very well.
Keep on keepin' on!