IIRC, early on, when news media interviewed the employee/owner of the Precision Car place near that crime scene, he said he saw the officer's car that morning. The reporter asked him if the car was marked or unmarked, and he answered it was marked. The link to this interview is up thread, I am sorry I don't have it handy.
Yes, it was a Patch posted interview, IIRC. There was also some information floating out there in MSM that: he was on his way to work; yet more info about his personal vehicle which had been remarked upon as familiar pickup truck, by one of his many friends and admirers. Could he have been driving to work in his patrol car?
Also in that interview from the guy from Precision Car, he mentioned that an officer would check that area everyday. Don't know if it was the same officer everyday. Certainly didn't seem out of the ordinary that this area was checked.
LE doing rounds would be normal, showing presence in industrial areas routinely. That being said, whatever the three people he saw were doing, if it was a big drug deal going down or something, then they may not have been the most adept of dealers, it seems possible?
There's something in congruent about the idea of anything being worth sticking around for to kill him, unless he caught one of them briefly maybe? That could leave some DNA at the scene?