BRIDGNORTH, England (AP) — Liam Treadwell, an English jockey who rode a horse with odds of 100-1 to victory in the Grand National Steeplechase in 2009, has died. He was 34.

Treadwell’s death was confirmed by horseracing trainer Alastair Ralph, who said it was “unbelievably sad” and a “big shock.”

Police attended the home of Treadwell after his death, which is being treated as unexplained, Britain’s Press Association reported. Police said they did not suspect any third-party involvement.

Treadwell was riding in the Grand National for the first time when he guided Mon Mome to one of the most surprising wins in the history of the grueling race in 2009.

It was one of more than 300 winners in Treadwell’s career.

He retired from riding in February 2018, but returned to the saddle in March 2019.

Nick Rust, chief executive of the British Horseracing Authority, said the governing body was “devastated” to hear the news of Treadwell’s death. and said his victory aboard Mon Mome “cemented his place in racing folklore.”