Law enforcement sources tell TMZ ... Mo3 was shot just before noon Wednesday on I-35 in Dallas and was transported to a hospital, where he died from his injuries.

Our sources say the fatal shooting went down like this ... the gunman and Mo3 were both traveling northbound on I-35 when the trigger man got out of his car and approached Mo3's. The rapper got out of his car and started running, with the gunman giving chase, firing multiple rounds and hitting Mo3 in the back of the head.

We're told the gunman also shot an innocent bystander who was sitting in his vehicle, and the second gunshot victim was transported to a hospital with non-life-threatening injuries.

The Dallas-based rapper claimed he'd survived a shooting last year. He was also arrested back in 2017 in connection with a Dallas-Fort Worth nightclub shooting that left one person dead.

Mo3 is most famous for his 2019 collab with Boosie Badazz, "Errybody (Remix)." He released a couple new songs earlier this year and has recorded 3 albums.

He was 28 years old.