What Causes Sudden Unresponsiveness, Eyes Rolling Back, Left-sided Tremors And Mouth Drooping?

Hello, my husband just had an episode that concerns me. He is resting now but I would like to know what happened. He was talking to me then became unresponsive. His eyes rolled back in his head, the left side of his mouth dropped, lips were white, face was pale, left arm and hand were shaking, he then collapsed to the floor. I held him and he was sweating but his left side was ice cold as was both hands. He eventually came to and didn t remember what happened. He felt weak and tired. I put him to bed and he is now sleeping. What do you think caused this to happen?