- Coleman pleaded guilty to charges of assault causing death and common assault in August.
- Davidson, a former surfing legend, was praised by Kelly Slater after his death.
- His family described the devastation caused by his death as "unforgivable."
The court heard that Mr. Coleman claimed he had attacked Davidson to protect the local community, alleging that Davidson was a convicted child sex offender.
Judge Peter McGrath criticized Mr. Coleman for taking the law "into his own hands".
"He was judge and jury of Mr Davidson. Tragically, Mr Coleman also became Mr Davidson's executioner," he said, according to the Australian Associated Press, which also reported that Davidson had been convicted of indecently assaulting a 15-year-old girl in 2017.
Mr. McGrath added that Mr. Coleman had developed a "fixation" with Davidson because, to his "knowledge and belief", he was a "repeat abuser" of "young females".
In the lead-up to the attack, Mr. Coleman had called Davidson a "pedophile" several times after seeing him approach a 19-year-old girl at the bar.
The 43-year-old pleaded guilty to charges of assault causing death and common assault in August. Receiving his sentence on Friday, he said he was "haunted" by his crime.
"[When] I realized what I'd done. I wanted him to wake up, to regain consciousness," he told the district court, the ABC reported.
Davidson first shot to fame in 1996 when he famously beat surfing legend Kelly Slater in two consecutive heats as a wild card entry into the Rip Curl Pro at Bells Beach in Australia. After his death, Mr. Slater paid tribute to the former athlete as "one of the most naturally talented surfers" he knew.
In a victim impact statement last year, his family described the devastation caused by his death.
"He spent all of his life surfing and a shark never attacked him but a human shark took him," his sister said.
"We can never forgive and forget and this incident should never have happened."
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