Phil Spector, the legendary producer whose “Wall of Sound” technique helped define pop music of the 1960s, has died of causes related to COVID-19. He was 81.

The Rock and Roll Hall of Fame member was serving 19-years-to-life in California prison for the 2003 murder of actress Lana Clarkson and was at the California Health Care Facility when he reportedly contracted the coronavirus four weeks ago. He was then transferred to an area hospital where he appeared to have recovered enough in order to return to incarceration. Recently, however, he relapsed and his symptoms returned, prompting officials to return him to the hospital where he died on Saturday, TMZ reports.

The California Department of Corrections confirmed his passing as a result of natural causes at 6:35 p.m. on Saturday. A coroner will determine the exact cause of death.

Harvey Phillip Spector was born on December 26th, 1939 in The Bronx, NY where, at the age of eight, his father killed himself and his mother soon after relocated him and his sister, Shirley, to Los Angeles. It was here that he attended Fairfax High in 1954 and formed relationships with future songwriters Jerry Leiber and Mike Stoller, with whom he would work later in life.

Spector began his prolific music career as a musician and reached early success with the Teddy Bears, who scored a number one hit in 1958 with “To Know Him Is To Love Him”. The song, written by Spector, was inspired by the epitaph on his father’s tombstone. The Teddy Bears disbanded shortly thereafter, and after his band the Spectors Three failed to take off the following year, Spector began a songwriting career where he apprenticed with his old friends Leiber and Stoller from high school.

He began his producing career in the 1960s working with acts like the Top NotesRay PetersonCurtis Lee, the Paris Sisters, and many more. It was with The Crystals‘ recording of “He’s A Rebel”, however, that Spector started to receive recognition for his production abilities. Followed by work with The RonnettesIke & Tina Turner, and more, Spector perfected the “Wall of Sound” technique that cemented him as a defining member of the music who didn’t actually play any of the music himself. His techniques would go on to be mimicked most notably by Brian Wilson on notable Beach Boys records including Pet Sounds and the ill-fated Smile sessions.

By the end of the 60s, however, Spector had largely disappeared from the music world as the makeup of popular music had shifted. His last major credits came in 1969 with John Lennon‘s “Instant Karma!”, which ultimately led to the decision by The Beatles for Harrison to assemble the tattered remains of their final sessions into the band’s last album, Let It Be, which proved to be a smashing success. This lead to Spector’s involvement in George Harrison‘s 1970 solo record All Things Must Pass as well as Lennon’s Plastic Ono Band and his much less successful 1972 record Some Time in New York City.

After a near-fatal car crash in 1974, Spector became increasingly reclusive throughout the decade. He resurfaced occasionally and worked with Leonard Cohen on 1977’s Death of a Ladies’ Man as well as Ramones‘ 1979 album End of the Century, the latter of which was met with harsh criticism by punk fans. The period between the 1980s and 2003 saw prolonged inactivity from Spector as he faded from memory as the climate of music retired him to a relic of a bygone era. He was inducted into the Rock and Roll Hall of Fame in 1989.

In 2003, actress Lana Clarkson was killed at Spector’s mansion in Alhambra, CA. Spector maintained that the 40-year-old Barbarian Queen star’s death was an “accidental suicide” caused when she “kissed the gun,” though a panicked Spector can be heard on a 911 tape saying “I think I killed someone.” After his first trial ended in a mistrial in 2007, he was later convicted in 2009 and sentenced to 19-years-to-life. He was due to be eligible for parole in 2024.