Washington state law (I think, current. via Google). It would seem that the shooter has a legal leg to stand on. Personally, I think lethal force is only justifiable in the face of potentially lethal force.
RCW 9A.16.050
Homicide — By other person — When justifiable.
Homicide is also justifiable when committed either:
(1) In the lawful defense of the slayer, or his or her husband, wife, parent, child, brother, or sister, or of any other person in his or her presence or company, when there is reasonable ground to apprehend a design on the part of the person slain to commit a felony or to do some great personal injury to the slayer or to any such person, and there is imminent danger of such design being accomplished; or
(2) In the actual resistance of an attempt to commit a felony upon the slayer, in his or her presence, or upon or in a dwelling, or other place of abode, in which he or she is.
AND
Certain property is considered special and it is automatically a felony to steal such property. The Revised Code of Washington 9A.560.65 makes it a Class B felony to commit theft of any motor vehicle, regardless of that vehicle’s value. Under 9A.56.300, it is also a Class B felony to steal a firearm of any value. If more than one firearm is taken, the theft of each firearm is charged as a separate offense.
Read more: What Constitutes Felony Theft in Washington State? | eHow http://www.ehow.com/info_8484497_constitutes-felony-theft-washington-state.html#ixzz2UmW3WLnB
If you have quoted that word-for-word it seems this person would be in the clear. I mean it doesn’t say “violent felony” just felony. Clearly the shooter was acting to prevent a felony.
I must say I always get nervous about warming up the car unattended. Thieves steal cars when they aren’t running, this just makes it so easy for them.
But I grew up in NYC in the 70s, I always say I’d lock my car if it was parked in the grand canyon.