By Saturday afternoon, investigators were leaning toward the theory that the Spanish Fork teen fell or was pushed from a moving vehicle after they saw other evidence was strewn along about 150 feet of the road, called Arrowhead Trail.
"His falling out, it wasn't an unsound [theory]. It seemed possible or even likely," Cannon said. But the autopsy ruled that out he died because a vehicle hit him, according to a news release.
But none of the other teenagers who may have seen what happened that night are speaking to detectives.
Haun had been at a party at a Payson home hours earlier with other teenagers where they had been drinking, Cannon said. At some point, Haun left on his own and may have been walking back home to Spanish Fork, the sergeant said.
The sheriff's office said five or six teenagers could be witnesses, but none of them are talking, Cannon said. Some of the parents have even told investigators that their children are not going to talk, he added.
Still, detectives kept at it Sunday.
"There's a couple of people they're still trying to get ahold of and a couple of others they're trying to go back to talk to again," Cannon said. "Maybe they'll open up a little more."
The woman who found the teen on the road passed the same spot on her way to work about 2 a.m. and said the body was not there at that time. As a result, police believe Haun ended up in the road sometime after that.
Investigators have surveillance footage from a nearby building that shows a vehicle passing shortly before the woman drives by. They will work Monday to enhance that video to figure out the type of vehicle and who may have been driving.
Detectives are asking that anyone with information that might help them find the vehicle and the driver call the Utah County Sheriff's Office at 801-794-3970.