According to Polk County Sheriff's office, at around 5:10 PM, at the end of the regular workday, one of the drivers was moving his bulldozer up an embankment to "heavy equipment staging area" to park it.
But the front blade was elevated to a height of 3-4 feet, obscuring his view, deputies said; after reaching the top of the incline to level ground, he began turning the bulldozer, when he heard a loud crumbling sound. Looking back, he realized he had run over a temporary toilet.
He immediately ran back to see if anyone was inside; tragically, there was. Henderson was found unresponsive.
The site foreman called 911 and paramedics rushed to the site, but it was too late. Henderson died at the scene.
The medical examiner ruled the death accidental, Fox13 reported.
County officials said it was the first fatality in the site's history.
"The Landfill is a dynamic, industrial environment with movement of hundreds of trucks coming to unload and heavy equipment at the Landfill all day long," County Manager Bill Beasley said. "We have never experienced anything like this here."