If all goes according to plan, Timothy McVeigh's heart will beat for the last time on Monday at 8:10 a.m. ET.

His execution will be the federal government's first try at lethal injection, and its first federal execution since 1963, when it put Victor Feguer to death by hanging for the murder of an Iowa doctor.

McVeigh received the death sentence for committing the nation's deadliest terrorist act when he bombed the federal building in Oklahoma City, killing 168 people. He will die by the most common method of execution in the U.S., approved for use by 36 states.

While it may seem simple and painless—many states have switched to the lethal injection in recent years because it seems more humane—execution by lethal injection is a much more complicated process. If botched, it can lead to prolonged, even painful, executions.

'The irony in this country is that we don't kill people frequently enough to get good at killing people.'

Lethal injection uses three different chemicals sent through an IV into the bloodstream of the inmate to cause them to lose consciousness, to lose control of their muscles, and finally, to stop their heart. Here's a closer look at how McVeigh will die by this process:

The Preparation

On Monday morning, about a half hour before his scheduled 8 a.m. ET execution, McVeigh will be strapped onto a gurney in the execution facility or "death house" at the U.S. federal penitentiary at Terre Haute, Indiana.

The prison staff assigned to carry out the execution will fit McVeigh with an IV. Nurses fit patients with IVs hundreds of times during the course of a week. But execution technicians aren't as experienced, and this step can be the hardest.

A gurney similar to the one Timothy McVeigh will be strapped to for his execution, June 11, 2001.

"They have to make sure they have a good vein right away, and that it proceeds smoothly," says Deborah Denno, a professor of law at Fordham University Law School who writes about death penalty execution methods. "They've had many cases of the needle popping out of somebody's vein."

Denno says it is particularly difficult to find veins on prisoners who are IV drug users. But even with a non-user like McVeigh, she says, there can be difficulties. "The irony in this country is that we don't kill people frequently enough to get good at killing people."

Next, technicians will attach cups leading to an electrocardiogram to McVeigh's chest. An electrocardiogram measures the electrical activity of a person's heart, which surges with each beat and is represented on the screen by a jumping graph and a soft beep.

This tool is commonly used in hospitals to make sure a patient's heart is still beating, to make sure they're still alive. But this time, it will allow the prison staff to monitor McVeigh's heart as it beats, slows and eventually comes to a stop.

In the next step, technicians will fit McVeigh with a catheter and anal plug. He will lose control of his muscles during the execution, and this equipment will prevent him from defecating or urinating inside the chamber.

When the preparation is complete, the curtains will be opened to the audience. Unnecessary personnel will leave the chamber, leaving only a designated United States marshal, the warden, and the executioners.

This, then, is the scene that witnesses will see when the curtains are opened: McVeigh, strapped to the gurney, and the warden, marshal, and execution personnel assembled around him. The warden will give McVeigh a chance to speak his last words — he has reportedly chosen "I am the master of my fate," an excerpt from William Ernest Henley's 19th-century poem "Invictus" — and then will order the executioners to begin.

The Injection

Lethal injection is a three-step process. Each step, making the inmate unconscious, then relaxing their body, and finally, stopping their heart, is caused by sending a different chemical through the IV.

As sodium pentathol, the first chemical, is passed into McVeigh's veins, he will become sleepy. After the blood has circulated through his body twice, he will be unconscious. Commonly used as an anesthetic in surgeries, sodium pentathol has a strong tranquilizing effect on the body and slows the areas of the central nervous system—the control center of the body—that underlie consciousness.

A hypodermic needle will be used to insert the IV in McVeigh's arm.

Between 100 and 150 milligrams of the chemical is normally used during surgery, but as much 50 times that can be administered in lethal injection. But the drug isn't always successful, notes Edward Brunner, Eckenhoff professor of anesthesiology at Northwestern University. "It's a very fast-acting drug," he says. "It can wear off in five minutes sometimes."

After injecting sodium pentathol, the executioners will administer a second chemical, pancuronium bromide, which is also used in surgeries. "He won't be able to move any of his muscles, including the diaphragm," says Brunner. The drug blocks the ability of nerves to contract voluntary muscles, meaning everything from McVeigh's face, hands, and lungs, to his legs and arms will be paralyzed. His heart, however, is an involuntary muscle like the stomach and lungs, and will remain pumping.

Finally, a solution of potassium chloride will be passed into McVeigh's veins. Potassium chloride stops the heart by overloading it with potassium, a chemical the heart needs to run normally, but which is toxic above a certain level.

"Potassium chloride has an arresting effect at those levels," says Brunner. "Cardiologists use it to get a 'soft heart' that's not beating so they can operate—but they wash the solution away afterward."

Without any such relief, McVeigh's heart will stop beating entirely. At such high concentrations, the potassium will upset the electrical signaling that regulates the contraction of the heart, causing cardiac arrest.

As the electrocardiogram becomes silent, McVeigh's heart will stop. In less than ten minutes time, McVeigh will be dead, and the execution of an American terrorist will be complete.