The song is about some guy that Mikael heard about by his friend... And the guy was like insane so he locked his girlfriend, her friend and himself inside his apartment. He wouldn't let them leave and he cuts himself with a knife, starts to destroy stuff and threaten the girls to death. The girls ended up fine (don't about the weird guy though).
This is what he build the lyrics from. And I really think that he uses metaphors and like exaggerates the stuff a lot...