Night time sighting by two witnesses four miles south of Livermore witnessed in Alameda County, California

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In late high school (1990), a group of my friends drove out of Livermore, CA down Arroyo Road. The time of year was likely Spring or Summer as I do not recall it being cold. At the end of Arroyo at the time, or off a turn off, was a pumping station for the local reservoir. We parked in the street. The reason for this trip was a trek to the ruins of a former mental hospital. Unclear if there was a more direct road but Arroyo road was desolate and rarely used at that point. We thought it would be fun and had attempted this journey before but were never successful. I was driving one of the 2 cars. It was after dark. The other driver and I got out of the cars and turned towards the hillside behind us. I was shining a flashlight along the hill and almost immediately notice a tall furry brown creature walking on 2 legs from left to right for about 30 to 40ft. This was approximately 40 ft away. The other driver was next to me and I asked "Are you seeing what I am..." I couldn't finish the ...