Rock pioneer Lou Reed dies at 71

Patrick Ryan and Jerry Shriver | USA TODAY

Rock pioneer and Velvet Underground frontman Lou Reed is dead at 71.

Timothy Greenfield-Sanders, director of the feature documentary film Lou Reed: Rock and Roll Heart, confirmed Reed's death Sunday to USA TODAY.

Reed had a liver transplant in May, although a cause of death has not yet been released.

Best known for songs such as Sweet Jane, I'm Sticking With You, Sunday Morning and Pale Blue Eyes, the Velvet Underground was formed in New York by Reed and John Cale. The band released its landmark debut album The Velvet Underground & Nico in 1967, and was inducted into the Rock and Roll Hall of Fame in 1996.

Reed left the Velvet Underground in 1970 and began a flourishing solo career that spawned such hits as Walk on the Wild Side, Perfect Day and Dirty Blvd. Reed took home one Grammy Award during his career of nearly five decades, for best long-form music video in 1999 for Lou Reed: Rock and Roll Heart.

After divorcing British designer Sylvia Morales in the mid-'90s, Reed married O Superman performance artist Laurie Anderson in 2008. In recent years, he toured with his new band Metal Machine Trio and contributed vocals to Metric's 2012 album Synthetica.

Reed also collaborated with heavy-metal band Metallica on an album, Lulu, released in 2011. In an interview with USA TODAY, he said that he had received death threats from Metallica fans who were upset about the collaboration, even before the record was released.

"I don't have any fans left," Reed said. "After Metal Machine Music (1975), they all fled. Who cares? I'm essentially in this for the fun of it."

Celebrities and musicians took to social media to express their condolences.

Miley Cyrus simply wrote "noooooooooo notttttttttt LOU REED."

Actor Samuel L. Jackson, who had recently met Reed at the GQ Awards, said, "The music of my generation. Still Relevant!"

Singer Josh Groban shared a link to the initial Rolling Stone story, writing, "A sad day in music. RIP Lou."

R&B star Miguel tweeted "RIP Lou Reed," adding that he had just gotten to his phone and seen the news.

Actress Susan Sarandon mourned his loss, writing "NY lost one of its originals with Lou Reed's passing. So sad. RIP."