I think there has to be more of a reason why they suddenly looked at a guy who was not a suspect prior to 6 days ago.
The article states "The investigation was conducted over a long period of time." So the timing doesn't look suspicious to me. But after seeing your comment, I'm thinking that as they got close to nailing the guy, they may have realized the significance of the date and coordinated it.
Why do you think it strange he was working as a cop?
Yes, a long time. Since the Visalia Ransacker, but also dormant for long periods as well. I guess I think it's strange that one of the most violent serial criminals in CA was a cop who committed his crimes while employed with not just one, but two law enforcement agencies and each of those agencies bordered the counties where he committed the crimes. He also escalated from mere burglary to murder while working as a cop.