Birdman Under Criminal Investigation For Lil Wayne Tour Bus Shooting

It's ironic ... the day 'Carter V' was released, we've confirmed Birdman is under investigation for allegedly plotting to shoot up Lil Wayne's tour bus.

The Cobb County, GA D.A. tells TMZ they are indeed investigating the man who calls Wayne his son.

We're told Young Thug is also being investigated in connection with the shooting.

TMZ broke the story ... Wayne's tour bus took on gunfire in Atlanta back in 2015, after Wayne performed at a nightclub.

The shooting went down just minutes after the bus pulled away from the club.

No one was injured, but not for lack of trying.