I agree with Jim - get as much of it as you can off with a razor blade tool. Home Depot and Lowes carry a spray bottle of stuff for removing window tint, and it works well. You can use it on the actual tint and it will eventually soften and remove it (with the help of a razor blade tool), but it is better at removing the remains after you have already gotten as much off as you can. I have seen it around the window treatment aisles, and also at the end of one of the lawn and garden aisles (huh?).
We have some lovely purple tint to remove from the upper parts of some of the front side windows in the 310. Sigh.