Mike Shinoda and Dave Farrell have said they are "heartbroken" by the death of close friend and bandmate,Linkin Park frontman Chester Bennington.
Bennington, 41, was found dead in a suspected suicide, the Los Angeles County coroner has said.
Shinoda, 40, tweeted: "Shocked and heartbroken, but it's true. An official statement will come out as soon as we have one."
Hours before the news was announced, the band debuted a new video for their song Talking To Myself, taken from their latest album One More Light.
Farrell tweeted a link to the video, a montage of clips from their shows, and asked fans what they thought.
He later tweeted just one word, "heartbroken", after learning of his friend's passing.
The date of Bennington's death, July 20, also marks what would have been the 53rd birthday of one of his close friends, former Audioslave and Soundgarden singer Chris Cornell, who died in May this year.
LA County coroner spokesman Brian Elias confirmed that law enforcement had responded to reports of a death in the Palos Verdes Estates area in LA.
Elias said that the death is being treated as a possible suicide, but added that it is still under investigation.
American website TMZ first reported the news, saying the singer's body had been found at a private residence in LA.
The band recently performed in the UK on the European leg of their One More Light world tour, which saw them play to packed venues in London.
They released their seventh album, One More Light, in May this year and their first album, 2000's Hybrid Theory, propelled them to success as it went on to sell 10 million copies.
They have won two Grammy Awards, five American Music Awards, four MTV VMA Awards, 10 MTV Europe Music Awards and scores of other accolades.
The band has collaborated with many artists over the years including Jay-Z and, more recently, London grime star Stormzy for a track on their new album called Good Goodbye.
Stormzy posted on Twitter shortly after the news broke, writing: "I am heartbroken you do not know what someone's going through serious. Prayers up for your family right now my brother."
Warner Bros Records CEO and chairman Cameron Strang made a heartfelt statement about Bennington, whose band is signed to the label.
He said: "Chester Bennington was an artist of extraordinary talent and charisma, and a human being with a huge heart and a caring soul.
"Our thoughts and prayers are with his beautiful family, his band-mates and his many friends."
Rihanna also posted her respect for the artist to Instagram, writing: "Literally the most impressive talent I've ever seen live! Vocal beast!"
Other people paying tribute to the musician included actor Ken Jeong who filmed a Carpool Karaoke episode with Linkin Park last week, Dwayne "The Rock" Johnson, and Timbaland.
In April this year, while promoting their latest tour in London, Bennington opened up during a Q&A session following a playback of a few tracks from One More Light.
The singer spoke openly about his state of mind when they started working on the new album.
He admitted to "hating the world", adding: "I had a song in my phone at the start of the process called I Hate The World Right Now. "
"Mostly the suffering that I was bringing on was self-imposed. All these thoughts were stuck in my head. It was not healthy. I remember thinking that I wanted to be left alone."
Born in Arizona, he is survived by six children and his wife, Talinda Ann Bentley.
The band were due to continue with the North American leg of their tour next week.