He was broken.
He was broken by the news.
In the first example, is 'was' a linking verb or an auxiliary verb? The second example shows that adding a prepositional phrase ('by the news') evidences that 'the news' is performing an action against the subject, which shows that it is an auxiliary, but the first example could simply mean that he felt broken — there doesn't need to be a direct instigator.
I've been confused about this for a while, and searching online hasn't produced the answer I'm looking for. The problem was the absence of answers. Most resources address what linking verbs and auxiliary verbs are, but they don't highlight the overlap.