After the tragic death of his brother Thomas, a scarred Stuart Kelly has taken his own life, four years after he lost his “best friend” to an alcohol-fuelled coward-punch.

Stuart, 19, was found dead in Mona Vale in Sydney’s northern beaches area on Monday, after years of campaigning for a foundation in Thomas’s honour against drug and alcohol-fuelled violence.

The Thomas Kelly Foundation’s work proved a key factor in the NSW Government’s improved lockout laws and mandatory sentencing for alcohol-induced violence.

But as a result of the enactment, Stuart was the victim of bullying and endless hate mail, The Daily Telegraph reported.

His strong stance on the subject made him a target after lobbying in favour of the Sydney’s despised lockout laws, the paper reported.

Stuart Kelly and Thomas Kelly. Photo: The Project

Stuart spent just one night at his new home at the University of Sydney, St Paul’s College before deferring from his marine biology studies, as he reportedly struggled to cope with the torment.

He left to take up a rugby coaching role with his high school, The King’s School’s under-14 team.

The school’s headmaster, Dr Tim Hawkes said the community was in deep sadness following the news.

“It is with great sadness that I inform you of the death of an Old Boy of the School, Stuart Kelly. This is the second great tragedy to affect the Kelly family,” he said in a statement.

“The exact circumstances surrounding his death are not known, however, it is enough to know that we have lost a member of our community and therefore our thoughts and prayers go out to Kathy and Ralph Kelly and their daughter Madeleine.”

At a fundraiser for the foundation last year, Stuart spoke of the scar he carried as a result of his brother’s death.

“I look back at that moment: I was 14 years old, I was told by a stranger that my brother, my best friend, was going to die. Those few words would change my life forever,” Stuart said.

Thomas Kelly died after an unprovoked assault in Kings Cross. Photo: AAP

“That was three years ago. However I carry a deep scar that you cannot see.

“It’s always there, it never leaves. It sits below the surface of your skin and surfaces when you least expect it.

“Tom never deserved to die that night, it was not meant to be his time; in fact I now believe that it could and should have been avoided.

“Our family lost a son and brother.”

Thomas, 18, was out with his girlfriend on Victoria St in 2012 when a drunken Kieran Loveridge punched him in the head without warning.

Thomas died two days later in hospital from a traumatic brain injury.