Is that guy's dad really the Zodiac killer?

Question

(was he, I should say)

Answer 1

No   he was  just  visiting....  

he followed  you  there!!

Answer 2

EDIT:

No not a step-dad (if so then the DNA tests  will be useless)

I guess we will only find out after the DNA samples have been matched, but if they don't equilize, then there is the possibility that he could be his step-dad like you said. The evidence is just too compeling to rule out these two posibilities.