When chimps attack your taxi

...it's usually bad news:

The Sierra Leonean driver died as the chimps ripped his body apart, and three Americans were treated at a hospital for minor injuries, said Oliver Somasa, a top police official.

Looks like they're after a whole group:

Armed police were searching Monday for 27 chimpanzees, Somasa said, while four others had already returned on their own accord to the reserve.
Somosa said it was unclear why the chimps attacked or how they were able to escape.

I have two thoughts:

(1) People in a car that will move should be at little risk of chimpanzee injury. So I'm guessing this is sort of like bison attacks at Yellowstone, where people cross the line of safety.

(2) If a chimpanzee group can face down and kill humans armed with an automobile, imagine what australopithecines could have done!