They know from previous seizures. But that is just a sidenote. They knew it was a mirror and not the publishing server, so what did they tried to gain form taking a simple and plain mirror. It doesn't make sense and shows either a lack of understanding technical issues or they just wanted to attack or annoy indymedia. But again, all this might be explained with just plain misunderstanding, so lets speak about that no warrant was shown to the colo maintainer (if there is just a warrat at all, who knows nowadays). What about that? This is apparently a simple case of unlawful seizure, no matter of how you think about indymedia or SHAC (I have my personal opinion about that too). Please, just see the big picture here!

You have read that indymedia removed the personal data (as a part of their privacy policy) _BEFORE_ the police took their server? So there was no need to seizure. And they KNOW that no IPs are logged and that this was just a mirror with no usefull data on it. So yes, freedom of press was violated as the cops took a needed tool (server) and damaged the infrastructure of indymedia.