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The alleged arsonist who was shot and killed by deputies in Rosemead Thursday morning was armed with a knife when she was killed, authorities said.

The woman, whose identity has not been released, was killed as deputies served a search warrant at her home in the 8700 block of Scott Street, the Los Angeles County Sheriff’s Department said in a news release.

In an update Thursday afternoon, officials said “a female adult was attempting to ignite the neighbor’s house on fire” when deputies were called to assist Wednesday night, and she barricaded herself inside her home.

During that barricade, the LASD was granted a search warrant for the premises, and when deputies went inside, the woman “was armed with a large knife,” prompting at least one deputy to open fire. The woman was struck by gunfire and taken to a local hospital, where she was pronounced dead.

“The weapon possessed by the suspect was recovered at the scene,” the update explained, adding that no deputies were hurt.

Anyone with information is encouraged to contact the LASD Homicide Bureau at 323-890-5500.

Call Crime Stoppers at 800-222-TIPS (8477) to provide information anonymously or visit lacrimestoppers.org.