By crikey but that was a nasty incident to be involved in!
As Forest Gump said: "Sh*t happens."

Not trying to be a sanctimonious smartass; but that was something I learned many years ago: Never work in the bush (woods to you Americans,) in close proximity to your mate.

One Sunday I was over the back of my farm clearing bush on my own. I stopped to refuel and heard another chainsaw going so went to investigate. It was Ronnie Oxenham, who was working for me at the time.
"What on earth are you doing here; it's your day off!"
"I got bored sitting at home, so thought I'd come and give you a hand."
"How did you get here?"
He pointed "Through there."
"Stay there and watch this."
I stepped up to an old man pukatea, scarfed it, started on the back cut, it fell on top of another couple of trees, they fell on to more trees which fell on to more trees...and so on.
WHUMP!
About 2 acres of trees went down in one go. I'd had a drive going, and that pukatea was the king.
And Ronnie had walked right through it. We wouldn't have found him even by smell.
He gave a me sickly smile and said "I'd wondered why you hadn't cut them all the way through."

A very salutary lesson. Since that day everybody on the place has strict orders to stay right away from anybody working with a chainsaw.
They're dangerous critters.