LOS ANGELES (AP) — A third man accused of plotting to attack Southern California military sites and other targets pleaded guilty Monday to a terrorism conspiracy charge in federal court.

Gregory Vernon Patterson, 23, entered his plea in U.S. District Court in Santa Ana to one count of conspiring to levy war against the U.S. government through terrorism. He also pleaded guilty to conspiring to use a firearm during that offense.

Patterson could face as many as 25 years in prison when he is sentenced in April, prosecutors said.

Two other men — Kevin James, 31, and Levar Haley Washington, 28 — pleaded guilty in the case last week. A fourth, Hammad Riaz Samana, has been declared mentally unfit to stand trial and is undergoing psychiatric care at a federal prison.