Very long story ahead!

Yesterday in the evening a friend of mine (calling him F from now on) became the target of something new to me...
Apparently one can fake his phone number through some fishy ways and call people with that number. Someone (we think we might know who it was, the why is at the end) did this yesterday to F.
Here's the whole story:
We were just talking together on a TeamSpeak Server (a program to talk to others on the internet) when suddenly another friend said: "F, why did you just call me three times in a row?" That was the first thing that was a bit suspicious. After that, F got calls from random numbers (even Afghanistan, we are German), and they said something like "Have fun with the police coming to your house". Then there was silence. 10 minutes later his phone rang and there were a ton of pizza delivery services in his town that apparently got pizza orders from him. Then there was silence, again. Suddenly someone with a hidden number called him, a woman's voice said they were the police and if F doesn't stop calling the police there will be consequences. F then told her what was going on but I think she didn't really care. She then wanted to know where F lives, but I told him not to say that, because if it is the police they can find it out by themself and if it's not, they don't need to know that.
Now, a short break: There is some fake information going around about where F lives. I can't remember when we found out but the attacker thought he would actually live there. No idea what happened at that location...
Now back to the story:
Time went by, nothing really happened. Suddenly F shouted: "There are blue lights outside! The police is here!" He muted his microphone and (the following is what he told us what happened) went down to the door (remember, he is 16) and there were two police men. They were asking about why he called the police. F explained what we knew until then, about number spoofing and stuff... They sent a more technical person to him, he understood what F was trying to explain. The police men drove away and he came back to tell us what happened. (Now we get back to what I heared myself.) The mom came in, screamed something that I couldn't understand, and F went offline. We searched who the attacker could have been. And we are pretty sure we found him. That guy connected to our Minecraft server (that's where I know F from) with his real IP, and his main account, which made it easy to search. He also got a static IP which means it doesn't change. We also got some information that in the recent days this guy was talking about VoIP spoofing and such stuff. Another friend of mine, a bit older, found some proofs and I think he will go to the police.

That's it. Thanks for reading.