Matthew McConaughey revealed in his memoir that his father James McConaughey died of a heart attack after having sex with the actor's mother, Mary Kathleen 'Kay' McConaughey. And now, the 55-year-old actor has revealed a strange new detail about the day his dad died in 1992. In an interview with The Guardian, Matthew said his mom insisted that her husband remain in the buff when paramedics retrieved his body. 'My understanding is that they made love that morning about 6:30am and as soon as they finished having sex he had a heart attack.' Matthew McConaughey revealed in his memoir that his father James McConaughey died of a heart attack after having sex.