Malcolm Young, guitarist and co-founder of AC/DC, died Saturday at the age of 64. Young had been suffering with dementia for the past three years, an illness that forced his retirement from the Rock and Roll Hall of Fame-inducted band he founded with his brother Angus Young in 1973. “Today it is with deep heartfelt sadness that AC/DC has to announce the passing of Malcolm Young,” AC/DC wrote in a statement.

“Malcolm, along with Angus, was the founder and creator of AC/DC. With enormous dedication and commitment he was the driving force behind the band. As a guitarist, songwriter and visionary he was a perfectionist and a unique man. He always stuck to his guns and did and said exactly what he wanted. He took great pride in all that he endeavored. His loyalty to the fans was unsurpassed.” The Young brothers lost their older brother George Young, the Easybeats guitarist and AC/DC’s longtime producer, in October at the age of 70. In an additional statement from Malcolm Young’s family, the band said that Malcolm Young died peacefully Saturday with his family by his side.

Young founded AC/DC in November 1973, and soon asked Angus to join when they were 20 and 18 years old respectively. They began national touring in 1974 with singer Dave Evans. AC/DC relocated to the UK in 1976, and began a heavy schedule of international touring and recording. The first six albums of the band were produced by ex-Easybeats members Harry Vanda and George Young, Angus and Malcolm’s brother, and they were also the production team behind the Marcus Hook Roll Band. After the death of lead singer Bon Scott in 1980, they recorded their biggest selling album Back in Black with singer Brian Johnson. Young missed the majority of AC/DC’s Blow Up Your Video World Tour to address his drinking problem. He eventually became sober and returned to the band. During his absence he was replaced by his nephew, Stevie Young with some fans not realising that he had been replaced as Stevie Young bears a striking resemblance to his uncle.

In April 2014, Young became seriously ill and was unable to continue performing. On 16 April 2014, AC/DC released a note stating that Young would be “taking a break from the band due to ill health”. On 24 September 2014, the band’s management announced that Young would not be rejoining the band. Stevie Young continued to fill in for Malcolm on the band’s 2015 Rock or Bust World Tour. On 26 September 2014, The Sydney Morning Herald reported that Young had dementia and had been admitted to a nursing home where he could receive full-time care. A source close to Young was quoted in this article as saying that he had “complete loss of short-term memory”. At the conclusion of the Black Ice World Tour, Malcolm was diagnosed with lung cancer. It was treated at an early stage, so surgery was successful and the cancer was removed. He also had an unspecified heart problem and wore a pacemaker.