James Gandolfini -- Tragedy Struck During Father-Son Trip

James Gandolfini's shocking death happened in the middle of a "guy's trip" for the actor and his teenage son, Michael ... TMZ has learned.

Multiple sources tell us James' trip was for pleasure and business -- first getting to spend some QT in Italy with Michael, who just recently graduated from the 8th grade ... and then attending the Taormina Film Festival in Sicily.

We're told Michael's mom -- James' first wife Marcy Wudarski -- immediately flew to Italy on Wednesday to be with her son ... after she was told James had died.

James and his son were very tight -- Michael is a big hockey fan, and he and his father were regulars at L.A. Kings home games.