Donald Henry Filippini, 89, of Los Altos, passed away on January 18, 2020, in San Jose, California. Affectionately known as Don, Donny, Dad, Grandpa, and “my sweetheart,” Don was born in Petaluma, California on June 10, 1930. Don served in the U.S. Army from June 1953 to June 1955 where he was stationed at Fort Bragg and in Germany. After graduating from UC Berkley with a BA in Mathematics he began his career as a high school math teacher. Don later earned his Master of Arts in Mathematics. Donald was a loving husband, a great dad, and a wonderful grandfather. He was loved by everyone who knew him as he had a kind heart and was willing to help anyone in need. Don was a true teacher and a true “MacGyver.” There wasn’t anything he couldn’t do or fix! Sometimes a bit slow for mom, but no one could have done it better! Don was a man of honor and respect. He stood for what was right and truthful. He would never bend the truth and was well respected for that. Don spent his working years as a high school math teacher in the Sequoia Union High School district.