07/16/2012 05:21 EDT | Updated 09/15/2012 05:12 EDT

Missing filmmaker promised to keep in touch

An American filmmaker making a documentary about B.C.'s rare kermode bear suddenly went missing last week after being in constant contact, his mother says.

"Since he started this trip, I spoke to him anywhere between one to three times a day," said Carla Sill from her home in Ohio.

She says it was a promise, the last thing her son Warren said, before leaving for northern B.C.

"He said, 'Mom, it's going to be okay. I'll keep in contact with you.'"

Warren Sill, 26, disappeared while filming a documentary about the Kermode, or "spirit bear" — a black bear with white fur — in the bush near New Hazelton, B.C.

"He has been interested in the wildlife since he was a pre-teen. Any Christmas gift, any birthday gift, was something about wild animals."

Police worry because the 26-year-old doesn't have wilderness experience and suspect he may be somewhere along the Whiskey Creek Trail near New Hazelton.

His SUV has been parked at the entrance to the trail since July 5, and his family last heard from him the day before.

Search and rescue, RCMP police dog services, an ATV, a helicopter and a number of volunteers are searching the area, which police describe as dense and challenging.

"They have kept us in the loop every step of this horrible, horrible nightmare," said Sill.

Warren Sill is described as a white male, about five feet ten inches tall and weighing around 180 pounds. He has a medium build and short dirty blond hair.

Anyone with information is asked to contact the New Hazelton RCMP at 250-842-5244 or call 911.