On 2017-01-15 22:39:30 +0000, David E. Ross said:

Location: Southern California, Sunset zone 21, US Department of
Agriculture zone 10b

Photo: http://www.rossde.com/test/Lindas_tree.jpg

My friend asked me to help her identify this tree. It is growing at the
house she recently bought. Note the clusters of small purple berries.
It does not look familiar to me. Is it familiar to anyone else?

It looks like an elderberry.