Many observers believe this could be Zodiac, but what is the likelihood.
The 6.30 pm time stated by Dr Rayfield and his son could be argued. Had this 'mystery man' been Zodiac, he would have had to return up the hill, get in his vehicle and drive 0.8 miles south to where Bryan Hartnell's Karmann Ghia was located. The time would be now approximately 6.33 pm. The walk to the crime scene location is a quarter of a mile. The average walking speed is 3.1 mph (1 mile taking approximately 20 minutes). Therefore the journey down to the location where Bryan Hartnell and Cecelia Shepard were lying, considering the terrain, would be likely above 5 minutes, but we will go with this figure. The time is now 6.38 pm. He hides behind a tree and prepares for his attack (6.39 pm). The Zodiac then entered into a fairly long dialogue with the couple, proceeded to secure them with bindings and then stabbed them multiple times. The minimum estimation is 10 minutes, taking us to 6.49 pm. Returning up the hill and writing on the car door, a minimum of 6 minutes. This would be now be 6.55 pm. The journey time for the 27 mile trip to the 1231 Main St, Napa payphone is estimated at 45 minutes. This would place Zodiac at the payphone at 7.40 pm, the exact time of the call. This timeline however is very optimistic, and does not tally exactly with the time of the attack, written on the car door by Zodiac, as 6.30 pm, but is nevertheless within 10 minutes.
Let us assume then, that Bryan Hartnell and Cecelia Shepard arrived and parked up the Karmann Ghia around 5.30 pm.
Dr Clifton Rayfield had reported that he had parked up four-fifths of a mile further north at 6.30 pm, likely one hour after Bryan Hartnell had arrived. So Detective Ken Narlow's assumption that Zodiac was probably "stalking any singular parked cars along the route." would be unlikely, as Zodiac would certainly have stumbled across the Karmann Ghia first, not Dr Rayfield's vehicle. This could lend credence to the idea that Dr Rayfield and his son saw the killer after the stabbing of the couple, hence the observation of a man wearing a "long-sleeved dark shirt with red coloring," that may have been blood. This however has a massive stumbling block. If the Zodiac Killer had discovered the Karmann Ghia first and parked alongside it, why would he be wandering around a hillside 0.8 miles north. He would simply have entered his vehicle and driven south towards Napa.
This would mean Dr Clifton Rayfield and his son saw Zodiac roughly 20 minutes after they parked their vehicle, as opposed to just after 6.30 pm. Or the actual time they arrived at the lake was nearer 6.50 pm. If this were Zodiac, it may explain the "red coloring."
Dr Clifton Rayfield had driven from Cypress Way, Los Gatos, California, so he would have traveled northwards along Knoxville Road. Had Zodiac's vehicle been parked further north, out of view, this would explain why Dr Rayfied and son had claimed they "had not observed a vehicle parked in the area of their car." But this would have put greater pressure on the already strained timeline of Zodiac leaving this area and committing any subsequent attack on Bryan Hartnell and Cecelia Shepard south of this location. This coupled with the fact Zodiac wrote 6.30 pm on the Karmann Ghia, strengthens Dr Rayfield's initial assumption, when he stated, "I didn’t realize 'Zodiac' came upon us just before he stabbed the young couple. I sort of assumed I saw him making his getaway." If this was the Zodiac, then he was likely making his getaway, and therefore never parked alongside the Karmann Ghia of Bryan Hartnell. If it wasn't Zodiac, then what you have just read is inconsequential.
LAKE BERRYESSA-NORTH OF THE CRIME SCENE [PT1]