50 Cent -- Caught Up in Mall Fight ... Bodyguard Under Criminal Investigation

50 Cent's bodyguard allegedly attacked a man and his son in a shopping mall -- a man who was trying to film the rapper -- and now cops are conducting a criminal investigation.

Law enforcement sources tell TMZ ... 50 and his son were at the Burbank Town Center Sunday when Lazzeri Frazier and his son saw 50 and thought it would be cool to shoot some cell phone video.

We're told 50's bodyguard came from behind Frazier and snatched the phone out of his hands. Frazier verbally confronted the bodyguard and the bodyguard then allegedly hauled off and shoved Frazier. The 2 began fighting and Frazier's 16-year-old son stepped in to break up the fight. The son claims the bodyguard punched him in the face.

The bodyguard fled the scene by the time cops arrived. 50 refused to speak to police, but witnesses corroborated Frazier's story.

Cops tell us the case will be sent over to prosecutors. 50 is not a suspect.