SALINAS, Calif. (AP) — The man accused of fatally shooting a central California police officer during a traffic stop last weekend has pleaded not guilty to murder.

The Monterey County District Attorney’s Office says Gustavo Matias Morales was arraigned Tuesday on a murder charge with a special circumstance for killing a police officer. Salinas Police Officer Jorge David Alvarado was killed during a shootout that erupted after he pulled over a car late Friday.

Morales was arrested when he showed up at Salinas Valley Memorial Hospital with a gunshot wound. Investigators have not said what was the traffic violation or what led to the shootout.