It happened at Carousel Park in Pike Creek around 12:17 p.m. Monday.
According to investigators, 68-year-old James Hagerty was preparing to cut grass on a hill near a pond when his tractor slid back down the hill, went over an embankment, and overturned into a creek bed.
Hagerty was pinned under the tractor and pronounced dead at the scene.
Immediately following the accident, County Executive Chris Coons and other officials say they went to Hagerty's home to express their condolences to his wife and children.
"We are all deeply saddened by this tragedy," Coons said in a statement. "This is a huge loss. Mr. Hagerty was a dedicated part of our family who worked so hard to serve the public."
The accident remains under investigation.