Sally Struthers was seen in public on Monday … weeks after her “All in the Family” costar Rob Reiner and his wife Michele were brutally murdered in their Brentwood home.

Sally was snapped out and about in Los Angeles … and her mood appeared to be glum … understandable given the recent double killings that rocked Hollywood.

TMZ broke the news … Rob and Michele were butchered in their home on Dec. 14 … and their son Nick has since been arrested and charged with their murders.

Sally is arguably best known for her work opposite Rob on the landmark “All in the Family” 1970s sitcom in which the pair played husband and wife, living under the roof of her parents, Archie and Edith Bunker. Her character, Gloria, was often caught in the middle of the hilarious arguments between her husband — Meathead — and father, played by Carroll O’Connor.

Among the countless fans and industry collaborators most recently paying their respects to Rob and Michele was Martin Scorsese … who penned an essay for the New York Times published on Christmas.

Martin said he bonded with Rob over being New York transplants in Hollywood and retold some jokes Rob made at various dinner parties over the years … and he praised Rob’s directing and acting skills.