Security help

[#1]

This might sound like a strange request but....
My son has a small server for Minecraft which him and a few of his friends use, recently another server operator decided he wanted my son to close his server down or he would Ddos? it until it was unusable. My son rightly told him he wasn't taking the server down so the kid told him he would take down my home internet too, 5 minutes later our internet dropped to a speed that meant we couldn't use it, Exactly when this kid said it would.
Is there anything I can do to stop this happening, I understand I can't do much about my boys server but my home internet is really important to us.
Thanks for any advice.

[#2]

Get the police he can be done under the computer misuse Act

[#3]

I suggest contacting the CSC (0800 432 0200) if this continues. The additional DDOS traffic could be affecting Plusnet's network.

[#4]

If you have a dynamic IP address, make a note of what it is http://whatismyipaddress.com/ and turn on you firewall logs and let them run for about a minute then stop, as if its a serious DDos there will be thousands of hits in just a minute.  Make sure you save those logs and then turn off your router and leave it for 10 minutes and power back up with a new IP address.
As suggested pass that info onto PN and the police.

[#5]

Thanks for the advice. Things seem to have calmed down but if anything happens again I'll be contacting the police.