See the Police Press Release for the details - but why throw the kittens out the window? Too much trouble to go to an animal shelter or take one of a host of other alternatives?
Originally published 9/1/11. Too quick to judge? Restored faith in humanity. Update 9/23/11: "Society investigators now say the kittens probably crawled into the vehicle's undercarriage and fell out as the owner drove to work. No animal abuse charges are planned." [Oregonian].