Prosecutors filed six murder charges Monday against a 28-year-old man accused of a shooting rampage north of Seattle.

Isaac Zamora faces six counts of aggravated first-degree murder, punishable by either death or life in prison without parole. Skagit County Prosecutor Richard Weyrich has 30 days to decide whether to seek the death penalty.

A sheriff's deputy, two residents, two construction workers and a motorist were killed in the Sept. 2 shooting spree near Alger, about 70 miles north of Seattle. Most of the shootings took place in an isolated neighborhood; prosecutors allege Zamora then headed south on Interstate-5, firing as he went.

Six counts of attempted first-degree murder were also filed, involving four people wounded by gunshots or stabbing and a couple who escaped injury when a bullet shattered two windows of their vehicle on I-5. In all, prosecutors filed 20 charges in Superior Court, including weapons and burglary counts.

Zamora was also charged earlier this month in District Court. His only comment during that court appearance was to twice declare: "I kill for God. I listen to God."

His attorney, Keith Tyne, said at that time "clearly there are significant mental health issues at play." A phone message left for Tyne late Monday was not immediately returned.

According to court documents, in a police interview after his arrest Zamora refused to discuss his specific actions but said God told him what to do.