A grizzly bear expert says fatal attacks such as the one on a woman and her baby in Yukon are unusual and it's important to have a thorough investigation into what happened.

The Yukon Coroner's Service said Valerie Theoret, who was 37, and her 10-month-old baby Adele Roesholt died Monday in the Einarson Lake area near the Northwest Territories boundary.

The service said a call came in about 3:45 p.m. from a trapper, Gjermund Roesholt, who said he was charged by a grizzly bear about 100 metres from a cabin Roesholt shared with his wife and infant daughter.

He said he shot the bear dead before finding the bodies of his wife and baby just outside the cabin.

Chris Servheen, who was the grizzly bear recovery co-ordinator for the U.S. Fish and Wildlife Service for 35 years, said it's unusual to see a fatal grizzly bear attack.

"It's most unfortunate, particularly where a woman and child were involved," he said in an interview from Missoula, Mont. "It's a very sad state of affairs -- something that no one likes to see happen -- and that's why it's important to understand what it was that was going on here.

"It would be valuable to try to understand why it happened, if that can be determined through a careful re-creation of the events."

Servheen, who has investigated the last eight fatal grizzly bear attacks in the United States, said it could be a number of scenarios.

"It could be a surprise encounter where perhaps they were walking around the cabin and a bear was coming around a corner and they surprised a bear at close range," he said.

"It could be a case where a bear was hungry and seeking food around the cabin and perhaps looking for something to eat. It could have tried to attack them and prey on them. There have been cases like that in the past."

Those theories could be sorted out with an investigation that looks at the movements of the people and the bear, he suggested.

Servheen said the investigators should also look at the condition of the bear.

"Was he in poor shape? Was he old? Did he have bad teeth?" he said. "Those types of things can give you information about the potential motivation of the bear."

He added that male bears and those in poor shape are often the last ones to go into their dens for the winter.

"A bear that is not in good shape tends to not want to go into the den and is still out looking for food. They become stressed looking for food at this time of year," said Servheen.

The coroner's office said its investigation into the deaths of Theoret and her child is ongoing.

The RCMP, its forensic identification section and the Yukon government's Environment Department are assisting.