Article says, "Someone identified only as "a close friend of a Steelers player" said that the reason Roethlisberger had a bodyguard was because of an incident where a man put a gun to Roethlisberger's head because Roethlisberger was involved with the man's girlfriend."
Roethlisberger wasn't a popular Steeler, even before all this - Shutdown Corner - NFL Blog - Yahoo! Sports