Famed rapper Project Pat's son has died after a shooting in a Tennessee park -- though the details around the incident are still murky ... TMZ has learned.

Patrick Houston Jr. -- son of the rapper and nephew of Three 6 Mafia co-founder Juicy J -- was killed last week in Imogene Heights, a historically Black Memphis neighborhood.

Memphis Police say the shooting went down just after 1 PM Friday ... and, when officers arrived at the scene, they found Houston dead.

No other details have been released yet.

Project Pat rose to prominence in the 1990s as a member of the group The Kaze ... joining the group in 1998, the same year they dropped their debut album.

The Kaze -- also known as Killa Klan Kaze -- were an associated act of Three 6 Mafia for years, owing to Pat's relationship with his little brother Juicy J.

Pat has one gold-certified album by the RIAA titled "Mista Don't Play: Everythangs Workin" released in 2001 ... just months before Patrick Houston Jr. was born.

Houston's funeral service is set for Saturday. We've reached out to law enforcement for more information about the shooting ... so far, no word back.

Patrick Houston Jr. was 21.

RIP