L.A. County sheriff's detectives are trying to determine why a woman armed with a butcher knife and a kitchen knife allegedly stabbed four people, one of whom is in critical condition.

The assailant was identified as Layla Rosetta Trawick, 35, from Antioch, Calif., authorities said. She was stopped by an off-duty deputy shopping at the store, Clay Grant Jr., who is assigned to the Men's Central Jail in downtown Los Angeles, Capt. Michael Parker said.

“We are exceptionally proud of Deputy Grant,” Parker said. “The reason why this tragic situation wasn’t worse was because of the quick thinking of an armed, off-duty sheriff’s deputy who was willing to risk his life to end this situation.”

The stabbing set off a stampede among customers, authorities said.

Deputies with the sheriff's West Hollywood station responded after numerous 911 calls reported a gunman at the Target at La Brea Avenue and Santa Monica Boulevard, Sgt. Josh Mankini said.

But it turned out a woman had stabbed four people in the store and was holding a bloody knife when the off-duty deputy confronted her and ordered her to give up the weapon, Mankini said.