It all went down in Justin's home town of Millington, Tenn., where JT rescued the Big Creek golf course from developers back in November.
The construction worker was involved in a renovation project clearing trees with a track hoe, when a tree fell and crushed him.
Shelby County Fire Dept. told WREG in Memphis: "We think at this point that the ground can be so unstable. It's very wet and very muddy that the bottom of the tree just gave way."
Calls to Timberlake's people have not been returned.