Police say 59-year-old Tina Werner of Felton, Kent County was standing on a platform, waiting to descend on a zip line.
It was at this point, police say, she fell from the platform to the ground.
The fatal accident occurred around 2:35 p.m. Wednesday at the Go Ape Tree Top Adventure attraction at the Lums Pond State Park, located at 1068 Howell School Road in Bear.
Authorities say paramedics had to perform CPR en route to Christiana Hospital where she was pronounced dead.
Other guests - some veterans of zip lining - were saddened and shocked about how something like this could have happened.
"I mean it's very safe, the equipment is very safe," said John Lunsford of Bear, Delaware.
According to the company's website, Go Ape offers a tree-top adventure experience, featuring a 2-3 hour journey through the forest canopy.
This as you take on suspended obstacles, Tarzan swings and breath-taking zip lines with an incredible view of the park.
"The staff basically takes you through how to hook up to the wires and everything as you're going across all the obstacles," said Lunsford.
"To me it's always been very safe, and it's a super fun activity around this area for sure," said Tara Altenritter of Bear, Delaware.
Lunsford says he could imagine how it's possible for someone to fall.
"I could imagine, yes. I mean if they didn't go through the precautions of hooking themselves up with the carabiners, lost their balance and fell whatever point on the platform, it could be possible," said Lunsford.
"I mean I could see how it could happen as just a complete accident," said Altenritter.
In a statement, Chris Swallo, the director of Go Ape, says, "Our thoughts and prayers go out to her family and friends and in particular to those who were on the course with her at the time."
No other injuries were reported.
Werner's body has been turned over to the Division of Forensic Sciences where an autopsy will be performed.
The investigation is ongoing, but police say foul play is not suspected.