Pete Seeger, an American icon who helped shape the modern American folk-music movement, died on Monday at the age of 94. He was known as much for his banjo-strumming music as he was for his political activism.

Seeger who wrote songs like “If I had a Hammer,” “Turn, Turn, Turn” and “Where Have All the Flowers Gone,” died of natural causes at New York Presbyterian Hospital where had been admitted six days ago, his grandson, Kitama Cahill-Jackson, told NBC News.

“He got the world to sing,” Cahill-Jackson told NBC News. “I think he was a role model to his family, to the whole world.”

Seeger, who was born on May 3, 1919, attended Harvard with plans to become a journalist before dropping out and moving to New York. He was an active member of the Communist Party in the 1940s and was a long-time supporter of the labor movement, and spoke up and sang in support of the civil rights and anti-Vietnam War movements.

Seeger's anti-war song, “Waist Deep in the Big Muddy” with its refrain, “The big fool says to push on,” became an anthem of sorts for protesters of the Vietnam War. And, according to the Los Angeles Times, Seeger once said: “I’d really rather put songs on people’s lips than in their ears.”

According to reports, former President Bill Clinton spoke of Seeger as “an inconvenient artist who dared to sing things as he saw them.”

Seeger won a Grammy Award for best traditional folk album in 1997 for his album “Pete” and won another in 2009 for his album “At 89.” In 2011, Seeger won a Grammy in the children’s music category for “Tomorrow’s Children.”

Following the announcement of his death, many people took to Twitter to pay tribute to the iconic Seeger.

Jeremy Corbyn, a British Labor Party politician, wrote on Twitter: “Very sad to learn of passing of Pete Seeger; a legend who inspired millions to believe in peace and themselves - music and song will live on.”

Michael White, associate editor of The Guardian, wrote: “Pete Seeger dies, one of the good guys, persecuted but vindicated by events & the affection/admiration of millions.” 

Singer Gretchen Peters wrote: "Woke up in the middle of the night to the news that Pete Seeger is gone. That's how you do it. Sing, love, live, give. Goodbye Pete."

Activist Leonard Peltier wrote on his Twitter account: "It is with Great Sadness we say goodbye to our dear friend and supporter Pete Seeger- Although we know he will..."

Writer Neil Innes wrote: "I am so sorry to hear of Pete Seeger's death. But what a life! We must never forget that he stood for all things Woody Guthrie. RIP."

Singer Cara Dillon posted on her Twitter: "The passing of a giant. RIP Pete Seeger."

Filmmaker Michael Moore wrote while posting a picture of Seeger: "It's Oct 2011, I'm on a NYC street, I look up & here comes Pete Seeger leading an impromptu Occupy march down B'way!"

Actor Troy Baker wrote: "One of America's greatest voices went silent tonight. Rest in Peace, Pete Seeger. Your contribution to the world will echo for generations."