Fatalities are relatively rare and when one occurs, it serves as a reminder that amid all the street parties and revelry associated with San Fermin, running with fighting bulls weighing 1,300 pounds (600 kilograms) or more on cobblestone streets packed with people is a life-risking exercise.

This run, the fourth of eight held at San Fermin, was by far the most perilous of this year's festival. The previous three runs were comparatively placid affairs, with no serious injuries.

The six bulls covering the half-mile (850-meter) course with six accompanying steers tend to mind their own business and keep running as long as they stay in a pack. A bull that gets separated is more likely to get frightened and aggressive, and that is what happened Friday.

Capuchino, a brown, 1,130-pound (515-kilogram) specimen, fell early in the run and ended up on its own.

When it reached a stretch right outside the bullring that marks the end of the course, it started charging right and left, and even ran back the wrong way several times. Runners scurried for safety to wooden barriers along the route as the bull attacked. Herders waving sticks tried in vain to guide it into the ring, even yanking on the animal's tail to turn it around.

This went on for a minute and a half, which is a long time at San Fermin.

At one point the bull picked one man up with its horns and flipped him into the air, then kept going after him as he lay curled up on the ground, covering his face. He got up and ran away, and was apparently not seriously hurt.

Jimeno Romero was killed by the same bull at a stretch slightly before this one.

"It was a light bull. Its charges were not particularly strong but it moved very fast from left to right," one of the herders, Humberto Miguel, told The Associated Press. "Of the whole pack, it was the one that gave us the most trouble."

The bulls used in Friday's run, from a ranch called Jandilla, have a reputation for being fierce at San Fermin. They hold the record for the most gorings in a single run — eight, one day in 2004.

The bulls used in the runs face matadors and almost certain death the same afternoon in the Pamplona bullring.