That happened to one of my clients.
She ahd been with her boyfriend, and she had got dressed and almost out the front door, when he called her back in. They were both in their early-mid thirties bTW.
The bedside lamp was on. Next thing you know, while she was atop her guy, she noticed he looked rather blue. She was given directions over the phone by paramedicas, to rescusitate him. She got his hear started, enough for his family to come and say their goodbyes while he was still 'alive', but he was brain dead. He died within hours.
I understand she never heard the end of it at his funeral. From his friends, that is, saying to her, "We knew you wee good, but you didn't have to kill him!
Guess they weren't practising 'safe sex'