"Mama, I just killed a man."
vs.
"Mama, just killed a man."
I'll ignore the blasphemy on the GREATEST SONG AND BAND OF ALL TIME!!11But why would it be "Mama, just killed a man" with a comma. That would only make sense if some guy named Just killed a guy. Either that site is wrong or Queen are idiots.
Basically, a "," in song lyrics indicate a pause, not necessarily a change in subject. Taking the rest of the songs context into account, it is as if the singer was saying "I killed a man" there regardless. Which explains why the lyrics are so often misquoted; the "I" isn't actually in the lyrics, it's just inferred...
"Mama!"
"Just killed a man!"
The speaker is indicating that he just killed a man to his mother. "Just killed a man" has a gapped subject.
Here's the video, listen for the "Mama, (I?) just killed a man..." at 1:00.Mama, just killed a man
Put a gun against his head
Pulled my trigger, now he's dead
Mama, life had just begun
But now I've gone and thrown it all away
Mama, ooo
Didn't mean to make you cry - Speaker made his mother cry; wouldn't make sense if she killed a man.
If I'm not back again this time tomorrow
Carry on, carry on, as if nothing really matters
http://www.youtube.com/watch?v=fJ9rUzIMcZQ