Cornell, who had been on tour with Soundgarden, died Wednesday night in Detroit, a representative for the singer said.
Law enforcement officials told ABC News that Cornell was found by a family friend who did a well-being check on the singer around midnight at the MGM Grand Detroit hotel. The wellness check was requested by Cornell's wife, according to Detroit police spokesman Michael Woody.
The family friend forced open the hotel room door and found Cornell on the bathroom floor, Woody said. The Wayne County Medical Examiner's office determined Cornell committed suicide by hanging.
VIDEO: Chris Cornell pumps up the crowd during show shortly before death
Brian Bumbery, a representative for Cornell, told the Associated Press in a statement that Cornell's death was "sudden and unexpected," and that the singer's wife and family are in shock.
News of Cornell's death prompted scores of tweets expressing sadness. Aerosmith guitarist Joe Perry tweeted: "Very sad news about Chris Cornell today. A sad loss of a great talent to the world, his friends and family. Rest In Peace."
Very sad news about Chris Cornell today. A sad loss of a great talent to the world, his friends and family. Rest In Peace. pic.twitter.com/BlgxE6cJLH— Joe Perry (@JoePerry) May 18, 2017
I AM SO SADDENED BY CHRIS CORNELL PASSING. @soundgarden— GAVIN ROSSDALE (@GavinRossdale) May 18, 2017
TOTAL SHOCK.GREAT MAN.GREAT BAND.GREAT LOSS. LOVE TO EVERYONE IN HIS WORLD. XXX
MORE: Chris Cornell's death sparks outpouring of grief
With his powerful, nearly four-octave vocal range, Cornell was one of the leading voices of the 1990s grunge movement with Soundgarden, which emerged as one of the biggest bands out of Seattle's emerging music scene, joining the likes of Nirvana, Pearl Jam and Alice in Chains.
Soundgarden broke through on mainstream radio with the album "Superunknown," which debuted at No. 1 on the Billboard 200 and was nominated for a Grammy for Best Rock Record in 1995. It included hit singles "Spoonman," ''Fell on Black Days," ''Black Hole Sun," ''My Wave" and "The Day I Tried to Live."
Tuesday, Soundgarden posted archival footage of the bandmates, including Cornell, getting a bite to eat while on the road. The caption of the post was a quote from Cornell: "What I look forward to the most -- because I tour so much, especially the last couple of years, by myself -- is the camaraderie. It's what we missed when we weren't a band."
Soundgarden disbanded in 1997 due to tensions in the band, and Cornell pursued a solo career. In 2001, he joined Audioslave, a supergroup that included former Rage Against the Machine members Tom Morello, Brad Wilk and Tim Commerford. The band released three albums in six years and also performed at a concert billed as Cuba's first outdoor rock concert by an American band, though some Cuban artists have disputed that claim.
Audioslave disbanded in 2007, but Cornell and Soundgarden reunited in 2010 and released the band's sixth studio album, "King Animal" in 2012.
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The Associated Press contributed to this report.