Q. You are working in the emergency room. A 36 year-old man presents with the "worst headache of my life". He reports that while at work, as a mechanic, he felt a sudden "thunderclap" in his head (about an hour ago) and he has a 10/10 headache now. While talking to you, he says that he is getting profound double vision (diplopia) and he is getting extremely nauseated and vomits profusely. His brother reports that this is all very unusual for the patient, that he never has headaches. He has not taken any new recent medications and does not take any medications normally. The patient does not do any illicit drugs. While you are evaluating the patient, he suddenly slumps over. You quickly assess the patient and find that his pupils are fixed and dilated and there is papilledema on his fundoscopic exam. You alert the attending that you think the patient is having which of the following conditions (most likely)?