My son in law does investigative work on complex cases.
The shear amount of data they have to sift through is staggering. And that is when they are looking at “known” individuals; they went through this stuff not even knowing what they were looking for.
They probably knew who this guy was for a while. Tracking him down probably took a couple weeks.
In the press conference, Moscow Police Chief James Fry said that they had received 19,000 tips and conducted 300 interviews.
Imagine running 19,000 tips to ground! And, after sifting through all of that, connecting the dots on the few relevant pieces of information.