The song tells of a boy who has committed a murder, and has been sentenced to death, OR maybe about a boy who commits suicide.
The opening line “is this the real life, is this just fantasy?” could be after he has committed suicide, and is experiencing the afterlife. This also shows with “look up to the skies and see,” where he is talking about entering heaven.
“I just killed a man”, he might be talking about himself in third person. Because he wasn’t thinking clearly before he pulled the trigger, he now feels guilty and confesses to his mother.
When he discusses leaving everyone behind, and facing the truth it is possibley talking about his personal religious judgment. He also says he doesn’t want to die, which could mean that he hasn’t faced the fact that he is dead yet. He also wishes that he’d never been born at all, fairly typical of comments made by suicidal people. This would also explain his words, “nothing really matters”
In the next scene, It could be God(s) judging him, and sentencing him to hell (which would explain the thunderbolts and lightening, and devil, Bismillah (in the name of God).
Scaramouch means cowardly, Fandango to do a foolish or useless thing, Beelzebub is another word for the Devil
Most of these ideas have been taken from other interpretations, especially potatoski