A Charlotte, N.C., man was charged with first-degree murder of a 79-year-old woman whom police said he scared to death. In an attempt to elude cops after a botched bank robbery, the Associated Press reports that 20-year-old Larry Whitfield broke into and hid out in the home of Mary Parnell. Police say he didn't touch Parnell but that she died after suffering a heart attack that was triggered by terror. Can the fugitive be held responsible for the woman's death? Prosecutors said that he can under the state's so-called felony murder rule, which allows someone to be charged with murder if he or she causes another person's death while committing or fleeing from a felony crime such as robbery—even if it's unintentional.

But, medically speaking, can someone actually be frightened to death? We asked Martin A. Samuels, chairman of the neurology department at Brigham and Women's Hospital in Boston.

[An edited transcript of the interview follows. Thanks to AHCJ_Pia for the story suggestion.]

Is it possible to literally be scared to death?
Absolutely, no question about it.

Really? How does that happen?
The body has a natural protective mechanism called the fight-or-flight response, which was originally described by Walter Cannon [chairman of Harvard University's physiology department from 1906 to 1942]. If, in the wild, an animal is faced with a life-threatening situation, the autonomic (involuntary) nervous system responds by increasing heart rate, increasing blood flow to the muscles, dilating the pupils, and slowing digestion, among other things. All of this increases the chances of succeeding in a fight or running away from, say, an aggressive jaguar. This process certainly would be of help to primitive humans, but the problem, of course, is that in the modern world there is very limited advantage of the fight-or-flight response. There is a downside to revving up your nervous system like this.

How can the fight-or-flight response lead to death?
The autonomic nervous system uses the hormone adrenaline, a neurotransmitter, or chemical messenger, to send signals to various parts of the body to activate the fight-or-flight response. This chemical is toxic in large amounts; it damages the visceral (internal) organs such as the heart, lungs, liver and kidneys. It is believed that almost all sudden deaths are caused by damage to the heart. There is almost no other organ that would fail so fast as to cause sudden death. Kidney failure, liver failure, those things don't kill you suddenly.

What exactly happens in the heart when it's flooded with too much adrenaline?
Adrenaline from the nervous system lands on receptors of cardiac myocytes (heart-muscle cells), and this causes calcium channels in the membranes of those cells to open. Calcium ions rush into the heart cells and this causes the heart muscle to contract. If it's a massive overwhelming storm of adrenaline, calcium keeps pouring into the cells and the muscle just can't relax.

There is this specially adapted system of muscle and nerve tissue in the heart—the sinoatrial (SA) node, the atrioventricular node, and the Purkinje fibers—which sets the rhythm of the heart. If this system is overwhelmed with adrenaline, the heart can go into abnormal rhythms that are not compatible with life. If one of those is triggered, you will drop dead.

What is an example of one of these deadly heart rhythms?
In most cases, it's probably ventricular fibrillation that causes these sudden deaths from fear. Ventricular fibrillation basically causes the ventricles (lower chambers of the heart) to vibrate in a way that hampers their ability to deliver blood to the body.

What other emotional states besides fear could lead to these fatal heart rhythms?
Any strong positive or negative emotions such as happiness or sadness. There are people who have died in intercourse or in religious passion. There was a case of a golfer who hit a hole in one, turned to his partner and said, "I can die now"—and then he dropped dead. A study in Germany found an increase of sudden cardiac deaths on the days that the German soccer team was playing in the World Cup. For about seven days after the 9/11 terrorists attacks on the World Trade Center and Pentagon there was an increase of sudden cardiac death among New Yorkers.

Who is most likely to suffer from sudden death?
A predisposition to heart disease would probably increase your risk of sudden death, but it happens at all ages and can happen to otherwise healthy people.