ANCHORAGE — A 16-year-old boy has been charged as an adult with first-degree murder in the death of a woman along a popular Anchorage hiking trail.

Kayden McIntosh is also charged with evidence tampering in the death of 19-year-old Cynthia Hoffman.

Hoffman’s body was discovered bound with duct tape in the Eklutna River near Thunderbird Falls. She had been shot in the back of the head.

Police say McIntosh and an unnamed woman who was a friend of Hoffman used Hoffman’s cellphone after the shooting to text Hoffman’s family and mislead them about where she was last seen.

McIntosh remains jailed. Online court documents do not list an attorney who could provide a statement on his behalf.

A relative of Hoffman called police Monday to report her missing. The person told police she had last been seen Sunday by a friend at Polar Bear Park in east Anchorage.

However, that information was incorrect, according to investigators.

Police say Hoffman, the adult female friend and McIntosh had driven Sunday to the Thunderbird Falls trailhead about 25 miles north of downtown Anchorage. A 1-mile hike along the Eklutna River leads to the falls, where river water tumbles 200 feet.

The three walked to the riverbank below the falls, where McIntosh and the woman bound Hoffman with duct tape, police said.

A fight broke out, and McIntosh shot Hoffman and pushed her into the river, police said.

McIntosh and the woman then drove to Polar Bear Park and used Hoffman’s phone to send text messages to Hoffman’s relative stating that she had been dropped off at the park, police said. Then they drove to Lions Park in northeast Anchorage and burned Hoffman’s belongings, police said.

On Monday, a relative of Hoffman’s female friend told police that Hoffman may have been shot but she didn’t know where.

Police on Tuesday interviewed the friend and McIntosh. The friend was released.

The investigation is the second involving a fatal shooting and a juvenile suspect on Sunday.

An 18-year-old man was killed and a boy wounded in a forest along Chester Creek Trail north of Sullivan Arena. A 12-year-old boy faces charges in the juvenile justice system.