Earlier quoted context omitted.
It wouldn't be the first time the police/three letters agencies lie about how they identified/located a suspect to not leak potentially illegal surveillance processes
It seems far more likely to be a case of incompetence. Law enforcement actually has an extremely low rate of "solving" cases, especially if you exclude all the "solved" cases where the suspect is caught on scene or that end in a plea bargain (i.e. did not have to establish sufficient evidence in the first place). Ever since he got "caught" (if you can call someone literally telling the police where he is "the police…
I don't know about your country, but in my country if you look like the person shown on CCTV committing a crime, you're wearing the same jacket, you're carrying the same illegal gun, and you're carrying a handwritten manifesto justifying the crime?
That's enough evidence for a normal jury of normal people to convict. The cops don't really need to add any DNA or CSI woo, juries are capable of exercising common sense.
Only way there's reasonable doubt here is if the guy's carrying the first place trophy for the CEO shooter lookalike contest.