Can I get arrested/prosecuted for fraping a facebook page?

[pokefan]

Let me explain, my 13 year old cousin left his fb page open on my laptop, and being a 16 year old me and my friend decided to do the casual fraping, saying the usual stuff like "suck my c*ck" "youve a nice p*ssy etc.) anyways, the people who read them realised it was a frap and just ignored it, my cousin went home and that was that. however, my cousin turns out he was fraped just a few days before, and his dad called the police and showed them the messages. they made a file about it and said they would look into it (trace the IP) anyways, after learning our little joke has gotten WAY outta hand, i told my cousin we fraped them this time. the dad told the police but doesnt know if they'll drop the case.
my questions are: Is there an actual crime committed (or that the police would bother pursuing)?
If there was, what would they do to punish a 16 year old, seeing as the person was 13.
I'm in Ireland also
I forgot to add though, that the worry is mainly of the content of the frape (sexual stuff, jokes obviously but they dont think so)

[Jason]

The police will not peruse the crime unless someone is willing to charge (Unless they get paid)

[Anjali]

That would be stupid because there are murderers out there and they should be focusing on murdersers and paedophiles