I am having some difficulties with this sentence: Los empleados de la tienda se quedaron perplejos.
Why is quedarse used here and not quedar? I went back to the lesson that deals with the differences and therein both are used with an adjective or participle to express the result of an action (=quedar) or change (=quedarse). For quedar + adjective, it is also written that the meaning is rather "to end up", and I feel like it fits well in the sentence above: they ended up perplexed due to what Beru did.
Could both be correct in this context?