Complex sentence: He ran into the Vulture, who was rejuvenated and attempting to kill all who knew him as an old man; he mistook Rick for Hobie and was unconcerned about the mistake.
Split into simpler sentences: He ran into the Vulture, who was rejuvenated and attempting to kill all who knew him as an old man. Vulture mistook Rick for Hobie and was unconcerned about the mistake.