Louis was reported missing on Wednesday ... with family members saying he was last seen Tuesday leaving his dad's house driving a gray 2014 Hyundai.
Now, their worst fears have come true ... Nix has been found dead, according to his mom.
Details surrounding Louis' death are unclear ... but the Jacksonville County Sheriff's Office was seen pulling a car matching Nix's from a local lake on Saturday.
The JSO announced they "located Louis Nix" -- calling off the missing persons search -- but provided no additional information.
Back in December, Nix was shot in the chest during an attempted robbery in his hometown of Jacksonville.