A “fearless” Australian commando who went public three years ago about his involvement in an alleged war crime in Afghanistan has died.

Sergeant Kevin Frost is among hundreds of former and serving Defence Force personnel who have taken their own lives in the past two decades.

Last week the 45-year-old went missing near his Busselton home, and over the weekend his family confirmed that he’d been found but had “tragically passed away”.

Friends have paid tribute online to their mate “Frosty”, who they say was a “fearless”, “proud” and “witty” man.

His death comes as Prime Minister Scott Morrison says his government will consider calling a royal commission next year into veterans’ suicides.

In 2016 Sergeant Frost told the ABC he had helped to cover up the alleged murder of an Afghan prisoner.

“The particular incident that I was involved in resulted in the POW that I had captured actually being executed, murdered,” the commando recalled in a television interview.

“I can’t remember if he cut the cuffs off first or if he cut the cuffs off after he shot him. That’s the one point I can’t remember there, cause I wasn’t looking.

“I didn’t want to look. I turned around and the guy was dead. He’d been shot through the forehead.”

A month earlier, Sergeant Frost had given the graphic details to the Inspector General of the Australian Defence Force, who had just begun an inquiry into alleged war crimes committed during the Afghanistan War.

The secretive inquiry, being run by New South Wales Justice Paul Brereton, is continuing and there has been no public indication as to when it may deliver its final report.

We’ve lost another Veteran. The demons became too much. To Commando Kev Frost’s family & mates I pass on my family’s deep condolences @ScottMorrisonMP @AlboMP @adellabeaini pic.twitter.com/9wDiTFXOX9

— Luke Gosling (@lukejgosling) December 15, 2019

A family spokesperson confirmed Sergeant Frost also suffered from the side effects of the anti-malarial drug Mefloquine, which was trialled on soldiers during their service in East Timor.

“Typically the symptoms of that include, depression, anxiety, also quite severe cognitive impairment, so problems with memory and concentration and in some cases neurological disorders,” said Stuart McCarthy, a retired Army officer who was prescribed the drug in 2001.

“The individual is often misdiagnosed with post-traumatic stress disorder, so it’s very common for soldiers and former soldiers who experience those health problems to have a lot of difficulties getting the right medical care.”

Since 2001 more than 400 former and serving Australian Defence personnel have taken their own lives.

-ABC