You have the right to defend yourself with "reasonable force" if you're attacked, so long as you have a legal right to be where you are. If you're shot at while trespassing and shoot back, the law won't protect you, but if you're driving your car on a public street? You completely have a right to fire back. Now, let's be clear, that's not an ideal circumstance, and may not even be tactically sound, he might have been better off just stomping on the gas and roaring down the street.

Reasonable force is going to depend on what the prosecutor, judge, and jury decide. This is why you're entitled to a trial by a jury of your peers. Now I'll disclaim here: Not a lawyer, don't know the law in Washington State, but shooting back is not inherently illegal.