See the attached news story. A redwood sheds a branch in San Francisco.
cbs5.com - Woman Dead After Tree Falls On Her At SF Park
This case calls into question a variety of things.
1) What happened to the evidence (the broken limb)? Was is quickly cleaned up and disposed of?
2) Park tree - when was it last inspected? When was it last worked on? Who worked on it? Did they know the difference between a collar cut and a flush cut?
As I observe and study why trees fall apart, I find most (not all) limb failures were caused by man (either directly or indirectly) and not by Nature.
Sure, the occasional severe storm can topple or break even the strongest limb, fork, or entire tree, but the root cause of the limb or trunk failure can frequently be traced back to bad tree work.
More than 25 years ago, Shigo convinced me the "phenomena of summer limb drop" was probably caused by bad work. Over the next 4 months, I dissected 60 limbs that dropped without warning, usually in the evening and with no wind.
I found flush cuts at the base of 58 of 60 the limb failures - many were buried deep within the limbs.
Communities around the world have a legal responsibility to inspect and care for trees in public spaces. In my part of the world, the City has over 2,000 miles of street trees and 16,000 acres of park trees and about 8 employees to keep up with them.
Trees are neither inspected nor pruned on any kind of regular program.
The poor woman who died in San Francisco may have been the victim of poor work or a failure to inspect.
What you see happening in your community?