Remember yesterday's stabbing onboard a Muni bus at 16th Street and Mission? It turns out that the cause of such chaos was good-Samaritan behavior rearing its ugly head.

While riding the 14-Mission, a 50-year-old man received a few non-fatal but violent stabs to the chest after coming to the rescue of an elderly woman. It seems that she was slapped during an argument with the suspect -- "a white male, 25 to 30 years old with short, dark hair...wearing a white T-shirt and blue jeans, [carrying] a dark backpack" -- prompting the heroic intervention.

Will the altruistic ever learn? Still, give this man a medal or something.