The suspected gunman in the Saturday ambush killing of a Los Angeles County sheriff's deputy has pleaded not guilty by reason of insanity to murder with special circumstances.

Kevin Salazar, 29, was arrested on Monday.

During his arraignment on Wednesday, Salazar's attorney entered a plea of not guilty and a dual plea of not guilty by reason of insanity on his behalf. He is being held without bail and is scheduled to next appear in court on Nov. 7 for a preliminary hearing, ABC reports.

The three special circumstances alleged in the charges are that the killing was committed against a peace officer, the suspect was lying in wait and the firearm was discharged from a motor vehicle, Los Angeles County District Attorney George Gascón said during a press briefing Wednesday, calling it a "cowardly and senseless murder."

Under California law, if the defendant in an insanity defense case is found guilty, a trial on the issue of sanity would occur. If a jury finds the defendant was insane while committing the crime, the defendant would be committed to a state hospital or facility for treatment. If found sane, the defendant would be sentenced as provided by law.

If convicted, Salazar faces life in prison without the possibility of parole, Gascón said.