XXXTentacion was shot Monday -- TMZ has learned -- and an eyewitness tells us he appeared lifeless with no pulse.
The 20-year-old rapper was shopping for motorcycles in Miami and, as he was leaving the motorcycle dealer, a gunman ran up to his vehicle and shot him.
XXX was in his share of feuds ... but as far as we know there were no ominous fights between him and anyone else.
He's had serious legal trouble ... he's awaiting trial for domestic violence against his pregnant girlfriend.
XXX has had real success ... his last album debuted at #1.