Washington state has one of the most liberal laws on the use of force by private citizens. If the burglars were committing a felony and the business owner was attempting to arrest them, he is in the clear.
In fact, the law on the use of deadly force specificicallt states that private citizens have broader authority in the use of deadly force than eve law enforcement officers.
You can look it up if you want.
Washington State has an article in the state constitution that guarantees a person the right to bear arms in defense of self or others.
Pretty hard to confuse that one.
DK