LARIMER COUNTY, Colo. (AP) - The Larimer County District Attorney's office says Audra Brownell of Sparta, Mich. was killed on June 17 when a falling rock hit her in the head as she sat in the Knoll-Willows open space in Estes Park.

Prosecutors say the boy was with a different tour group than Brownell, and his bus was parked next to hers.

According to prosecutors, the boy went up to the cliff and kicked off a piece of rock that weighed more than 100 pounds. A piece broke off a rock that weighed about 30 pounds, and that is what hit Brownell in the head as she sat with her boyfriend.

Brownell belonged to the Rockford Reformed Church in Michigan and was visiting Estes Park on a backpacking trip.

Prosecutors do not believe the boy had any intention of hurting Brownell and are working with his attorney to come up with some sort of plea deal.

"From what we understand, he's a good kid from a good family," Larimer County District Attorney Larry Abrahamson said.

After Brownell's death, the Knoll-Willows area was closed for the investigation. It reopened in July. Fencing along the lower part of the area where the incident happened is still in place.

The area is in the green space behind the town hall parking lot in Estes Park.

After the incident, local residents told 9NEWS they had never heard of anything like this happening before.

The boy's name was not released because he is a juvenile