anyone ever had this happen?

my friend recently bought a walther ppk with a silecer from bass pro shops, he took it home and we took it out of the box and put the silencer on, he racked the slide and pulled the trigger. BANG it explodes all on his hand, his mom even had to take some pieces out of his hand. it was a spring pistol with 450 fps, anyone know why this happened? i have also heard of this happening to several other people with different guns from different stores? plz tell me.

I've heard about this but never had it happen. pretty much the plastic was crude and useless. stuff like this happening makes me paranoid to modify a gun.