A telltale pattern of vertically split wood on the branch that fell on a Vancouver city worker Thursday is crucial to the investigation into how he died, CTV News has learned.

That pattern – known as a “barber chair” in the forestry industry – can help explain why the heavy catalpa branch next to Connaught Park in Kitsilano suddenly snapped, crushing 43-year-old urban forester Jody Taylor.

“This is a sad day for the City of Vancouver. Yesterday was a real tragedy. Many people who work here are feeling the loss of Jody,” said Vancouver Mayor Gregor Robertson Friday morning at city hall, where flags are flying at half-mast.

The city and WorkSafeBC are now investigating what led up to Taylor’s death, the first workplace fatality in the city in at least 20 years. Taylor had been a city arborist for 16 years. He leaves behind a 10-year-old daughter.

“He was a man’s man, a big strong man with a big heart,” said Malcolm Bromley, general manager of the Vancouver Park Board.

The branch that fell appears to have split while Taylor was cutting it from the bucket of a cherry picker. In a “barber chair,” unstable wood under strain will separate, and the branch will fall unpredictably.

“Barber chair" incidents have killed five B.C. workers and seriously injured three more since 2008, WorkSafe BC records show.

While these incidents largely happen in rural forestry or farm settings, they are a concern to urban foresters, said arborist Mike McLellan with Tree People in Port Coquitlam.

“It’s when a loaded tree or branch under pressure is cut and the tree itself splits upwards,” McLellan said, adding that the tree’s shape can add to the risks. “The heavier the lean, the more inherent the risk is of injury or fatality.”

The B.C. Forest Safety Council said all wood types can “barber chair,” though some species, such as yellow cedar, spruce, alder and maple are more prone to the pattern.

Whether a tree will split depends on many variables, such as the wood type, the individual tree, and the cut made in the wood, and each “barber chair” incident must be investigated fully to understand what happened and why, the council added.

Taylor’s death is shocking his co-workers, who describe him as a great guy who was quick with a smile.

“He was a great dad, really devoted, he loved kids, he was a really amazing photographer,” said co-worker Sophie Dessureault.

Dessureault said she saw Taylor that morning at the Park Board office.

“He was good. He was happy. He came by, grabbed some chocolate – he emptied that bowl for me,” she said. “He was really quick to smile. He was always quick to laugh.

“It hurt us so deeply to lose him so unexpectedly and senselessly it seemed,” she said.

Vancouver investigators must produce a report to WorkSafeBC by Saturday. City manager Sadhu Johnston said the city will also produce a more fulsome report into the death in 30 days.