re:Police Helicopter in King County
It is actually the King County Sheriff's Office helicopter. Try listening to the Seattle/King Co TRS. They can come up on any talkgroup within the system and more! I just listened to them assisting Kirkland PD looking for a vehicle they lost in a pursuit! They are usually up flying between 8P and 4A (and that is by their discription). I also know they have gone down to Pierce County and assisted them.
Just listen for "Guardian 1" and I think they have a "Guardian 2" but I have never heard that call sign used on the radio. If you do have a 800 mhz scanner and can monitor that system, make sure you have the PSAP, LERN and MARS talkgroups programmed in as that is usually where they seem to come up first. If not, try VHF freqs of 155.370 and 155.190. These are the VHF frequencies for LERN and MARS respectfully.