Deemed the “Deacon of Death” by local media, a 61-year-old Belgian man is accused of killing 10 people – including his own mother – via air injection.

Ivo Poppe, a former nurse turned ordained pastor, was arrested in 2014 when he told his psychiatrist that he “euthanized” dozens of elderly people by injecting air into their blood, causing a fatal air embolism.

The case went to trial earlier this week. On its first day, he confessed to killing “between 10 and 20 – 20 maximum. That’s approximate but it’s around that number.”

An air embolism, also called a gas embolism, is a rare but potentially fatal condition. It happens when one or more air bubbles enter the vascular system through a vein (venous) or artery (arterial), causing a blockage. These bubbles can travel to the brain, heart, or lungs and result in a stroke, heart attack, or respiratory failure respectively.

Air can enter the veins or arteries in a variety of ways when injected via syringe, IV, or a catheter. Other causes include lung trauma, scuba diving, explosion, and blast injury, and – wait for it – blowing into the vagina. 

Doctors and nurses are trained to avoid allowing air to enter the veins and arteries during medical and surgical procedures, as well as how to recognize and treat one if it occurs.

The symptoms are similar to other ailments and as such can be difficult to trace. They include difficulty breathing, confusion or loss of consciousness, low blood pressure, blue skin hue, and pain in the joints, chest, or muscles.

If an air embolism is suspected, doctors will perform an ultrasound or CT scan to confirm or rule out its presence and find its exact location.

Treatment includes surgical removal or hyperbaric oxygen therapy – doctors place a person in a high-pressure room that delivers 100 percent oxygen, which shrinks the air embolism and allows it to be absorbed into the bloodstream without damage.

Poppe is being tried for 10 murders, but prosecutors believe he may have killed many more. They cite a list of deaths at the hospital that he recorded in his diary. Lawyers say he was just taking note of the deaths around him, but prosecutors allege at least 50 of them were suspicious.

According to reports, Poppe initially made partial confessions during the investigation, saying he was acting compassionately for those who were terminally ill. His 89-year-old mother, who suffered from depression, was the most recent death in 2011.

Belgium has one of the most permissive assisted dying laws in the world. Patients can seek approval with evidence of an “incurable” condition, mental or physical, that causes “constant and unbearable” suffering.

Poppe is also charged with the deaths of two great-uncles and his father-in-law (or step-father based on some reports).

The trial began earlier this week with dozens of witnesses, including relatives of the deceased.

If guilty, Poppo will be one of the most prolific serial killers in Belgian history.