June 6, 2014 -- Boston Internet pioneer Steve Johnson said he was convinced early on that his younger brother's death more than two decades ago was not a suicide, but murder –- the result of a gay-bashing incident in Australia.

In December 1988, Scott Johnson was celebrating the completion of his doctorate in mathematics and had everything to live for. But just days later, his naked body was found mangled on the rocks at the bottom of 164-foot-tall cliffs near Manly, just north of Sydney -- a hang-out or "beat" for gays.

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The 27-year-old's clothes were found neatly folded at the top of the cliffs, and his wallet was missing. After 36 hours, New South Wales police assumed the death was a suicide as there was no evidence of foul play.

"Scott and I were as close as two brothers could be," Johnson, now 55 and co-founder and CEO of the advertising company Choicestream, told ABC News. "He was a brilliant, idealistic young man. The day he died, he had just finished the final proof for his math Ph.D. He had just gotten off the phone with his professor who had congratulated him."

Family and friends were baffled because Scott had shown no signs of negativity or depression. Johnson was haunted by the death, not knowing if he had slipped or been pushed.

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As early as 1989, the family asked for an inquest to reexamine the death and Johnson made multiple trips to Australia to meet with police over the decades. But he says they faced a “Catch 22”: Without a reversal of the coroner’s report, police could not reinvestigate; and without evidence for murder, the coroner could not take that action.

At the time of his brother's death, Johnson was a graduate student with no money. But by 1998, he had made a fortune while at America Online, leading the development of AOL 4.0, You've Got Pictures and its acquisition of Netscape.

His 25-year quest to find his brother's killer is the subject of a documentary, "Australian Story: On the Precipice," which aired in 2013 on Australian Broadcasting Corporation's flagship show.

The film will be shown throughout June here in the United States on the World Channel, associated with PBS, as part of series of programs for Lesbian, Gay, Bisexual and Transgender Pride month.

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The 30-minute documentary resulted last year in the New South Wales Police re-opening the cold case and offering a $100,000 reward for “information on how [he] died.”

On a NSW police webpage devoted exclusively to the case, Detective Acting Superintendent Chris Olen says, "At this stage, it is not known whether Scott's death is a result of suicide, misadventure or murder. …With a lack of witnesses and physical evidence, this is a very challenging case. What we need is fresh information to help us solve this case and bring some closure to the Johnson family."

The case echoes the 1998 murder of 21-year-old Matthew Shepard, who was abducted by two men and tied to a split rail fence in Wyoming, where he was assaulted with the butt of a pistol and left to die. But in Shepherd's case, within a week police were able to make arrests.

His death sparked the eventual passage of the Matthew Shepard and James Byrd Jr. Hate Crimes Prevention Act, a federal law that targets hate crimes directed at lesbian, gay, bisexual or transgender people as well as by race, national origin and other factors.

"It's obvious Steve cared and loved his brother very much," Matthew's mother, Judy Shephard, 61, told ABC News. "I admire his tenacity greatly and I know what it takes to continue to do that when the odds are against you -– it was far worse than mine. I can't imagine what he had to go through all these years, wondering, and now to find out."

Scott Johnson's death is still a mystery, but his brother is convinced it was a hate crime.

A 2013 report in the Sydney Herald, says that it is believed as many as 80 men may have disappeared or been found dead possibly linked to so-called "poofter bashing" between the late 1970s and late 1990s, of which 30 remain unsolved. Packs of youths would ambush gay men and assault them, the story said, and they would "cliff jump" and push men over the edge.

As late as 2002, the director of the Australian Institute of Criminology said “poofter bashing” in Australia was often committed "as sport,” according to the online newspaper, The Age. “Apparently this sport is not only alive and well, but young men who excel at it can expect to be treated leniently by our courts.”

Today the term is used widely in the political debate over gay rights.

Scott Johnson left Sydney for the beach on a Thursday and his body was found on that following Saturday. "I know what Scott did," said his brother. "He put his pencil down and went to celebrate."

"He was a sweet, gentle person," said Johnson, still choking up 26 years later. "The atmosphere in these places was very friendly and open. To see someone up there who you expect to be friendly and suddenly be jumped –- I can't even imagine."

Steve Johnson first learned his brother was gay in high school. "Scott had a lot of trouble telling me who he was in love with ... I even thought that he was having trouble because he got a girlfriend pregnant."

"When he said it was not a girl, I was shocked," said Johnson. After graduating top of his class at CalTech and studying at Cambridge University and Harvard, his brother eventually fell in love and moved to Australia to study.

Johnson's quest for the truth began in 2005 when he said his "world was turned upside down."

An inquest in Sydney, "Operation Taradale" looked at three other unsolved deaths around the same time as Scott's death at nearby Bondi Beach, where bodies had ended up at the bottom of the cliffs. They, too, had been ruled suicides.

"One man had someone else's hair clenched in his fist," said Johnson. "It was pretty clear that happened to Scott."

Johnson flew to Australia after hearing about those news reports from his brother's partner, but he said police "completely ignored me."

In 2007, after several other futile visits, Johnson enlisted the help of Dan Glick, then at Newsweek, who had made his mark reporting the 1996 death of child beauty queen JonBenet Ramsey.

"If Steve wasn't wealthy, this would not have gotten investigated and that is a sad testimony," Glick told ABC News. "That's why I respect him so much."

Glick, co-founder of Colorado-based The Story Group, said he used his journalism skills as a private investigator, "asking good questions, having a really good bulls*** meter, not believing everything we are told and seeking documentation."

In the film, Glick tells Johnson, "I think Scott was killed. I will investigate it as if my own brother had been killed."

Johnson spared no expense in funding Glick's investigation and the pair became close friends. They created a Facebook page "Justice for Scott Johnson," hoping to find leads.

As a result of Glick's investigation, the coroner overturned the suicide verdict in Scott's death in 2012. At the time, Johnson was besieged by reporters and agreed to tell his story to the press. "It was on the 6 o'clock news that night and 15 or 20 articles appeared over the next week," he said.

But Johnson said police continued to "stonewall" him, maintaining the northern beach where Scott had died was not a gay hangout –- until the documentary aired.

The day after the film was broadcast, Johnson and his sister held a news conference with police to announce Scott's case would be reopened. Seven families who saw the show came forward to say they also had lost sons –- at least five at the beach.

Scott's partner, an academic, declined to be part of the documentary for privacy reasons. He now lives in the United States, according to Johnson.

Johnson admits the seven-year investigation could never have been accomplished without his financial backing, but other families still want answers.

He is pushing for broader investigations into other cases.

"These crimes are still solvable," he said. "These youth gangs are still in their 40s and probably live in the same cities. One thing about gang violence –- they like to brag. We've heard dozens of stories from former gang members or their girlfriends."

Records kept by the Lesbian and Gay Society Melbourne show that about two dozen men were convicted in the gay-bashing cases in the Bondi area and sentenced to prison terms from the late 1980s to 2009. The rest of the cases are still open.

Times have changed in Australia in regard to hate crimes directed against LGBT people, according to a recent report by the Australian Broadcasting Corp. “I would say that in Australia, in practice, we have achieved a remarkable degree of recognition and equality for same-sex partnerships,” author Dennis Altman told the network.

“Cops in general are much more aware and much better trained and much less homophobic,” said Glick. “But I talked to one cop who was openly gay in 1988, and he said it was not easy then.”

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Johnson has set up an email address for anyone with information about the case at justiceforscottjohnson@gmail.com