People start reporting the happenings as soon as the appearances begun. But they were brief and gradual enough that people just assumed the reports were wrong. Who could blame them? It is easy to explain those broken windows with something mundane. Couple of kids did it. A home burn down? There are probably thousands of those every day. Did that car looks like it was crushed under something that looks awfully like a foot the size of a man? Well, vandalism can get awfully dedicated these days. Did that security camera caught a shadow of something walking down the parking lot? CGI is so good these days!
Still it didn't take that long, comparatively speaking, less than two days after the first reports. It was necessary for the monsters to stay corporeal for long enough to cause too many havoc to be ignored. People that saw the videos on the internet by and large still thought that they were publicity stunts, but a police officer looking at a bus with a burning claw mark isn't going to think "some film studio is very dedicated to their production." It was rather good to avoid mass hysteria at least until the major attack on Austin. The thing was a storm of ice blades rotating around a dark humanoid shade. It only manifested for ten minutes, but it damaged several city blocks and sent the entire capital to a panic. When the second attack came, there were more people dying in stampedes than by the monster's ice blades. Not that that weren't victims from the ice blades.
There isn't much that they can get from the data, but it is not nothing. The monster attacks appear to be more or less evenly distributed around the world with some bias towards population centers, but not enough to mean that major cities are the most likely to be attacked (at least for now). The monsters manifest progressively if the reports are accurate. Earlier manifestations are brief and less substantial, being only shadows. As time progress they get stronger, last more and develop individual traits. One was covered in chains and could control metal. One was a ball o blinding light. One looked like a huge elephant with plated armor made of ivory. One was reptilian and had snakes for arms. Being more solid makes them more dangerous, but has the upside of also making them more vulnerable to conventional weaponry. Which isn't saying much and they are fast. Once it looked like the "Hydra" was defeated, but it only faded away temporarily and then showed up fully healed three hours later,.
The monsters manifestations stick to more or less the same dozen miles radius, figuring out where the next monster is going to show up is currently impossible. But they have a report of an early manifestation, still on the "shadow humanoid" stage.