Video captured at a beach in the Mexican state of Baja California Sur shows the woman grabbing bags right out from under the animal.
People on the beach can be heard pleading with the woman to run away.
The bull gets aggressive, and attacks the woman. It continues for some time, worsening as the bull gets more and more aggressive.
It's unclear if the woman was injured.
Video from before the attack appears to show the same woman approaching the bull.
There are ranches near the beach, and animals often end up near the water.