Navy SEAL's chilling suicide note he taped to his door before shooting himself in his heart to preserve his brain - as bombshell study reveals chilling pattern on the brains of vets who committed suicide

A Navy SEAL's chilling suicide note has been revealed five years after he shot himself in the heart to preserve his brain.

Lt. David Metcalf took his own life inside a garage at his North Carolina home in 2019, arranging a stack of books about brain injuries by his side, the New York Times reports.

He also taped a note to the door, that read in part: 'Gaps in memory, failing recognition, mood swings, headaches, impulsiveness, fatigue, anxiety and paranoia were not who I was, but have become who I am.

'Each is worsening,' the 42-year-old wrote, before turning the gun to his heart and leaving his brain to be analyzed by the Department of Defense - which has since discovered an unusual pattern of damage it believes may have been caused by his own weapons.

Now, Metcalf's wife, Jamie, says she sees his sudden death as a way to draw attention to the problem affecting Special Operators.

'He left an intentional message because he knew things had to change,' she told the Times. 

Lt. David Metcalf took his own life inside a garage at his North Carolina home in 2019, leaving a letter behind describing brain issues he had been facing

His wife, Jennifer, would donate his brain to research by the Department of Defense

At least a dozen Navy SEALS have died by suicide over the past decade - either while in the military or shortly after leaving.

A review of their deaths has since determined that they all had a number of factors in common.

The average age of the deceased veterans is 43, and each was deployed to combat a number of times - but none had been wounded by enemy fire, according to the Times.

All of the veterans also spent years firing a range of powerful weapons, jumping from airplanes, blowing open doors with explosives, diving deep underwater and learning hand-to-hand combat.

Around the age of 40, nearly all of them started to struggle with insomnia, headaches, memory and coordination problems, depression, confusion and sometimes rage.

Many were also diagnosed with Post Traumatic Stress Disorder, but a Department of Defense study of eight of the soldiers found blast damage in the brains of every single one. 

Petty Officer David Collins also took his own life in March 2014

Collins' wife, Jennifer, was adamant about donating his brain to research and has been encouraging other Special Operations families to do the same

That brain damage apparently came from shock waves unleased by the troops' own triggers in an array of weapons, studies suggest.

The energy waves from a weapons blast surge through the brain and bounce off tissue boundaries like an echo, according to the Times.

For a few fractions of a millisecond, these waves create a vacuum that causes nearby liquid in the brain to explode into bubbles of vapor.

Those explosions are then powerful enough to blow braincells apart.

At first, there may be no noticeable symptoms - but as exposure continues, the effects may grow worse, according to Dr. Daniel Daneshvar - the chief of brain injury rehabilitation at Harvard Medical School.

He explained that brains can often compensate for the damage, until the injuries accumulate to a critical point when 'people kind of fall off a cliff.'

'People may be getting injured without even realizing it,' Daneshvar said. 'But over time, it can add up.'

Dr. Daniel Daneshvar said the effects may grow worse over time with repeated exposure

It is believed many suffered brain damage caused by shock waves unleased by the troops' own weapons

For Petty Officer David Collins, the repeated exposure led to confusion in the years before he took his own life.

Collins had spent 20 years working as a Navy SEAL, and was deployed to Afghanistan twice and Iraq three times. 

When he was not deployed, his wife said he was away from home for hundreds of days each year in training.

Combat never seemed to faze him, his wife Jennifer said, but toward the end of his career, Collins started to avoid social gatherings, struggled to sleep and started making obsessive family schedules - becoming irritated when they were not followed.

Simple chores like raking the leaves started to become a problem, Jennifer said, describing how we would walk out the door to go to work, realize he had forgotten his keys, go back inside to get them and forget why he returned.

His mental health then really started to take a turn at the age of 45.

He left the Navy and started a civilian job teaching troops how to operate small drones, but one morning, Jennifer said he called her in a panic from a work trip, saying he forgot how to do his job and had not slept in four days.

'He was super anxious, almost paranoid,' she recounted. 'He was nothing like my husband.' 

At the time, the military generally associated brain injury with blasts from roadside bombs - but Collins never experienced that. 

Doctors eventually diagnosed Collins with depression, anxiety and Post Traumatic Stress Disorder, and prescribed a number of drugs that didn't help.

Collins would then go on to take his life in March 2014. 

When police arrived at their Virginia Beach home to confirm his death, Jennifer said she was 'adamant' that she wanted his brain donated to research.

'I wanted to try to find some answers,' she said.

That donation marked the first for the Department of Defense's Brain Tissue Repository in Bethesda, Maryland - which had been set up two years prior to examine the brains of deceased veterans for clues about PTSD and traumatic brain injuries.

As researchers there pored over Collins' brain, they noticed that nearly everywhere that tissues of different density or stiffness met, there was a border of scar tissue.

'For the first time, we could actually see the injury,' Dr. Daniel Perl said, noting: 'If you know what the problem is, you can start to design solutions.' 

The Pentagon says it has a 'moral obligation to protect the cognitive health and combat effectiveness of our teammates'

They would go on to notice the same pattern in six of the eight Navy SEALs who took their own lives, as Jennifer convinced more and more families to come forward. 

By the time Metcalf died in 2019, brain donations had become somewhat common for Special Operations troops.

So after the lieutenant died, Jamie decided to donate his brain to research as well.

She has described how she noticed a sudden decline in her husband when he returned in 2018 from his fifth deployment.

He had been a high achiever, was an enlisted SEAL sniper and taught martial arts to other SEALs. A few years before he died, Metcalf also decided to pursue a military medical career, became an officer and sailed through a training program for physician assistants.

But he started to become confused and plagued by headaches, Jamie said, describing how he would put wet laundry in the dryer on top of dry clothes.

'It was so unlike him - he had always been so organized,' she said.

'Now I know he was afraid there was something happening in his brain, but at the time, I think he tried to hide it.' 

But researchers determined Metcalf and one other soldier had a different type of damage in the same area of the brain as the other SEALs.

Star-shaped helper cells in their brains, called astrocytes, appeared to have been repeatedly injured and grew into large, tangled masses that barely functioned.

A study on the astrocytes is forthcoming, according to the Times.

In the meantime, Rear Adm. Keith Davids, commander of Navy Special Warfare - which includes the SEALs, said 'we have a moral obligation to protect the cognitive health and combat effectiveness of our teammates.'

He said the Navy is trying to limit brain injuries 'by limiting blast exposure, and is actively participating in medical research designed to enhance understanding in this critical field.'