The man who held Paula Deen at gunpoint died from cardiovascular disease, a natural cause ... TMZ has learned.

Eugene Thomas King Jr. died from hypertensive and arteriosclerotic cardiovascular disease, the New York City Medical Examiner's Officer tells us.

According to the Mayo Clinic, hypertensive and arteriosclerotic cardiovascular disease is caused when high-blood pressure damages the arteries and causes plaque to build up. This is considered a natural cause of death by the M.E.

We broke the story ... King was found unresponsive in his Brooklyn apartment just after 5 PM on Thursday. Emergency Medical Service personnel pronounced him dead at the scene.

Back in 1987, King committed armed robbery ... and Deen, who was working as a bank teller at the time, says he held a gun to her head. He was caught and sentenced to 25 years in prison for that crime and another robbery.

In 2013 -- after Deen used a racial slur -- King came to her defense ... claiming she was being "persecuted" for making one small mistake in judgment and reacting out of anger. In the same Inside Edition interview, he apologized once again for holding her at gunpoint.

Eugene was 75.