Hello, My Brother Who Is 54 Years Old Recently Began

Hello,

My brother who is 54 years old recently began a weight training program with bench presses and biceps curls 2 months ago and was hitting it pretty hard. He suddenly developed severe muscle pain and weakness in both arms a couple of days ago and kept saying he felt his blood wasn't circulating in his arms. It stopped and then started again yesterday and one time involved his upper chest and he developed nausea. He went to the hospital and everything was negative for a heart attack and stroke. they couldn't find anything although they kept him overnight for observation. He takes lisinopril for BP and Creatine for his work outs. Do you have any idea what this could have been?