Updated

The California man charged after a weekend shootout with police on an Oakland freeway is due back in court next month after additional charges were filed against him.

Byron Williams faces four counts of attempted murder on peace officers, as well as enhancements for firearms, body armor and gang activity. He appeared in court Wednesday for a plea hearing but didn't enter a plea. Instead, he was ordered to return to court Aug. 11.

Prosecutors also filed two additional felony charges against Williams of being a felon in possession of a firearm.

The 45-year-old Williams was arrested after a gunbattle with 12 officers on Interstate 580 early Sunday. Police say he was planning an attack on the ACLU and another nonprofit group.

It's unknown whether Williams has been assigned an attorney. After-hours attempts to reach the public defenders' office were unsuccessful.