A horrified Lucas Machias sent me this link and several other sources confirmed it : A band of chimpanzees in a reserve had killed and eaten two young gorillas.
Lucas was as horrified as the writers, who stressed that this had never happened before. I am more cynical, as I suspect other people who have worked in zoos, are.
To make a short generalization: chimps are assholes. Faced with choices they always do the evil thing. Chimps regularly hunt and kill monkeys and a recent report is out about chimps killing an albino chimp apparently because it was different. They killed the gorillas because they could, and I bet it will happen again.
Gorillas are basically peaceful souls, if a bit morose (they are also vegetarian and wouldn’t eat a chimp anyway).
As far as I know, bonobos are very nice, and so are orangoutangs, although there are disturbing reports about adolescent male orangs practicing rape. Gibbons, though true apes, are more like monkeys in their behavior.
But as far as I’m concerned, chimps are assholes. In none of the other species a tame individual has ever ripped a woman’s face off. On a more benign level, consider two of the chimps I knew. One would shit in her hand and throw it at you; the other, more creative and younger, used to pursue you with shit, rub it on your pantleg, and then grab a dairy brush and spank himself with it laughing hysterically. He also could be far more dangerous — he ripped open the arm of a young girl so badly she needed stitches when her idiot mother tried to put her in the chimp cage when an escaped tapir was running hysterically around the main paths.
Of course, we share about 90% of our DNA with this Caliban. Sigh. (Actually the woman proved it true: she sued the zoo for letting a veterinarian sew up her daughter only to find he was the head of pediatrics at Mass General consulting on apes.)