What does it mean if after a workout you get dizziness, breathing difficulties, double vision & pins & needles?

Hi, I am a Personal Trainer and my friend has just text me saying that he was at the gym for a workout and after he said he went dizzy, had double vision, his throat tightened up and was gasping for breath, and had excruciating pins and needles in his arms and legs that were making his fists clench. What might this be? He carries out the correct breathing technique upon execution of each repetition. I dont have the knowledge to answer this question so I wonder if you might help? Kind regards, Paul