I googled "Report Virus Authorities"
and didn't find much. Almost all of the results looked like they would give me a trojan, but there was a link to Avast's site. On the Alwil Virus Report Form
one of the questions is 'Did you report the virus attack to the authorities?", but it doesn't actually say how. Maybe someone else could shed some light on this.
Oh, by the way, you said you know who sent it, but do they live closeby? Cause if you know the asshole who did it, why don't you just call the cops and say they were trying to "plant surveillance devices" on your personal property.