up until he killed the kid.

By such means we might say: "he was a such a super guy ..until the day he (insert monstrosity here)
Such is not all that uncommon with mass murderers or rampant peadophiles.

"It's the action that was out of bounds, it was his behavior, not his personality."

You'll have to explain to me how you differentiate the two.

And as this is a music site: He was a sweet and tender Hooligan: http://www.youtube.com/watch?v=ECSjeTAA2Uw