Bob passed on December 26, 2019.

As of February, 2020, there is no obituary online, but the link does lead to a "Tribute Wall."

https://www.eastlawn.com/obituaries/Robert-Charles-Cotter?obId=10179138

UPDATE: Bob's obituary is at:
https://www.legacy.com/obituaries/sacbee/obituary.aspx?n=robert-charles-cotter&pid=196791418

Here is the text: Thursday December 26, 2019 "Bob", father of 3 daughters passed away at age 77 from cardiovascular disease at home. Bob was born Feb 24 1942 to Wm. E Cotter and Mabel C (Chambers) Cotter in Sacramento California where his ancestors first settled in 1861 traveling across the plains. They were farmers at Walsh Station, later Deputy Sheriff, saddle makers and even a train engineer on the Mallet now in the Sacto. Train museum plus a captain on the Balcutha sailing ship now in San Francisco Maritime Museum. He attended C K McClatchy High School enrolling in the Navy at age 18 and served on the USS Helena later working as a laborer for the family business Cotter Electric for some years before leaving to have his own trucking concern. He dearly loved the outdoors, hunting, cutting firewood, camping and cookouts. He was preceded in death by his mother Mabel, father William, wives Susie and Joan. He was survived by brother William Richard Cotter, daughters Debbie Bolton, Terrie Pigeon and stepdaughter Kathy Kokkos, grandchildren Cassie and Brandon, 4 great grandchildren and cousins Eric and Peter Cotter, Frank (Jacque) and Linda Schetter. Private family graveside services were held at East Lawn Cemetery Sun. Feb 23, 2019.

https://www.eastlawn.com/obituaries/Robert-Charles-Cotter?obId=10179138