What has occurred here? (Piston failure)

Hi everyone, I have a doubt about what happened here. Engine it's an OE Ford zetec turbo (MK1 Focus RS) about 400bhp. It's the second piston (of 4).

I think that this occurs by a (damage?) oil spray nozzle, but the strange thing it's that other pistons has marks at the crown's outside, at the same zone and drag marks at the skirts. I think that the four spray nozzles can't not be damaged...

Thanks for your help.

This looks like the engine has been suffering from some pretty severe detonation. It's definitely not as a result of the oil squirters. I'd imagine that the crowns of the other pistons will be showing a sand blasted appearance around the same region that this piston is physically melted.

Ok Andre, thank you very much!

The crown's of the other pistons have drag marks at the outside. The pistons crowns(1, 3) has marked the cylinder wall. But only number 2 piston have damage like you can see at the pictures.