He wasn't breathing when he was found, but EMTs were able to find a pulse on Petty. TMZ updated their reporting to say that a source close to the singer alleged that Petty had "no brain activity" when he arrived at the hospital and was later pulled off life support.
TMZ reports that Petty's current condition is unknown, but he was immediately deemed in critical condition from the time he was discovered in his home. The outlet confirms that they've been "in touch" with sources close to the musician, who are "clearly upset but not talking."
The Los Angeles County Fire Department confirmed to People that they were dispatched to a Malibu home at 10:45 p.m. on Sunday night after receiving reports of an unconscious male.
See photos of Tom Petty:
Tom Petty through the years
Tom Petty through the years
UNSPECIFIED - JANUARY 01: Photo of Tom PETTY (Photo by Richard E. Aaron/Redferns)
UNSPECIFIED - CIRCA 1970: Photo of Tom Petty (Photo by Richard McCaffrey/Michael Ochs Archives/Getty Images)
UNSPECIFIED - JANUARY 01: Photo of Tom PETTY (Photo by Ian Dickson/Redferns)
UNITED STATES - DECEMBER 01: Photo of MUDCRUTCH and Tom PETTY; Posed studio portrait of Tom Petty (Photo by Jim McCrary/Redferns)
(Original Caption) Portrait of the man who made it big with 'The Heartbreakers' in 1976. (Photo by Neville Elder/Corbis via Getty Images)
NEW YORK: Tom Petty from Tom Petty and the Heartbreakers posed in New York in 1976 (Photo by Richard E. Aaron/Redferns)
Tom Petty and The Heartbreakers 1977 (Photo by Chris Walter/WireImage)
UNITED STATES - JULY 15: Photo of Tom PETTY and Tom PETTY & The HEARTBREAKERS; Tom Petty performing live onstage with Tom Petty & The Heartbreakers (Photo by Ebet Roberts/Redferns)
Tom Petty and the Heartbreakers perform at the Aragon Ballroom, Chicago, Illinois, November 23, 1979. (Photo by Kirk West/Getty Images)
UNITED STATES - JULY 06: PALLADIUM Photo of Tom PETTY and Tom PETTY & The HEARTBREAKERS, Tom Petty performing live onstage with Tom Petty & The Heartbreakers, playing Fender Stratocaster guitar (Photo by Ebet Roberts/Redferns)
LOS ANGELES: Tom Petty performs live in Los Angeles in 1983 (Photo by Richard E. Aaron/Redferns)
CHAMPAIGN - SEPTEMBER 1985: Musicians and songwriters Bob Dylan and Tom Petty pose at Farm Aid on September 22, 1985 in Champaign, Illinois. (Photo by Deborah Feingold/Getty Images)
Tom Petty performs on stage with Bob Dylan at Ahoy, Rotterdam, Netherlands, 19th September 1987. (Photo by Rob Verhorst/Redferns)
Tom Petty (Photo by Jeff Kravitz/FilmMagic)
Musician Tom Petty attending on 'ASCAP Music Awards' on May 15, 1991 at the Beverly Hilton Hotel in Beverly Hills, California. (Photo by Ron Galella, Ltd./WireImage)
Musician Tom Petty attending the re-naming party for 'Def American-American Records' on August 27, 1993 at the Hollywood Memorial Park in Los Angeles, California. (Photo by Ron Galella, Ltd./WireImage)
Musician Tom Petty attending 12th Annal MTV Video Music Awards on September 7, 1995 at Radio City Music Hall in New York City, New York. (Photo by Ron Galella, Ltd./WireImage)
CANADA - MARCH 17: Tom Petty (Photo by Ron Bull/Toronto Star via Getty Images)
Musician Tom Petty attending the world premiere of 'The Postman' on December 12, 1997 at Warner Bros. Studios in Burbank, California. (Photo by Ron Galella, Ltd./WireImage)
Musician Tom Petty attending 'Tom Petty and the Heartbreakers Receives Hollywood Walk of Fame Star' on April 28, 1999 at the Hollywood Walk of Fame in Hollywood, California. (Photo by Ron Galella, Ltd./WireImage)
Tom Petty during Tom Petty & The Heartbreakers Honored with a Star on the Hollywood Walk of Fame at Hollywood Boulevard in Hollywood, California, United States. (Photo by SGranitz/WireImage)
Tom Petty and Marilyn Manson at the premiere of 'Blow' at the Chinese Theater in Los Angeles, Ca. 3/29/01. Photo by Kevin Winter/Getty Images.
Tom Petty during 2005 Billboard Music Awards - Arrivals at MGM Grand in Las Vegas, Nevada, United States. (Photo by Jason Merritt/FilmMagic)
NEW YORK - NOVEMBER 15: Singer/musician Tom Petty attends the Museum Gala 2007 at The American Museum of Natural History November 15, 2007 in New York City. (Photo by Stephen Lovekin/Getty Images)
NEW YORK CITY, NY - NOVEMBER 14: Dana Petty and Tom Petty attend TOM PETTY and the HEARTBREAKERS Celebrate Their New Book RUNNIN' DOWN A DREAM to Benefit The Tipitina's Foundation at Milk Studios on November 14, 2007 in New York City. (Photo by DAVID X PRUTTING/Patrick McMullan via Getty Images)
HOLLYWOOD - APRIL 14: Rita Wilson, Eric Idol, T-Bone Burnett, Tom Petty, Jeff Lyne, Sir Paul McCartney, Joe Walsh, Olivia Harrison, Tom Hanks and Dhani Harrison attend the ceremony honoring the late George Harrison with a star on The Hollywood Walk of Fame on April 14, 2009 in Hollywood, California. (Photo by Lester Cohen/WireImage)
LOS ANGELES, CA - DECEMBER 31: Rock musician Tom Petty watches the game between the Los Angeles Lakers and the Denver Nuggets at Staples Center on December 31, 2011 in Los Angeles, California. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and/or using this Photograph, user is consenting to the terms and conditions of the Getty Images License Agreement. Mandatory Copyright Notice: Copyright 2011 NBAE (Photo by Evan Gole/NBAE via Getty Images)
Tom Petty and the Heartbreakers perform a benefit for KCSN radio at the Plaza Del Sol Performance Art Center on the campus of Cal State Northridge. (Photo by Robert Gauthier/Los Angeles Times via Getty Images)
Musician Tom Petty speaks at a ceremony where Jeff Lynne receives a star on the "Hollywood Walk of Fame" in Los Angeles April 23, 2015. REUTERS/Phil McCarten
Musician Tom Petty performs on stage after being inducted during the 47th Songwriters Hall of Fame Induction ceremony in New York June 9, 2016. REUTERS/Eduardo Munoz
Musician Tom Petty speaks to guests after being inducted during the 47th Songwriters Hall of Fame Induction ceremony in New York June 9, 2016. REUTERS/Eduardo Munoz
Musician Tom Petty performs at the 2017 MusiCares Person of the Year show held in his honor in Los Angeles, California, U.S., February 10, 2017. REUTERS/Mario Anzuoni
DEL MAR, CALIFORNIA - SEPTEMBER 17: Tom Petty performs in concert on the third day of KAABOO Del Mar on September 17, 2017 in Del Mar, California. (Photo by Gary Miller/Getty Images)
VANCOUVER, BC - AUGUST 17: Tom Petty of Tom Petty and the Heartbreakers performs on stage at Pepsi Live at Rogers Arena on August 17, 2017 in Vancouver, Canada. (Photo by Andrew Chin/Getty Images for ABA)
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Petty is coming off of a 50-plus show tour, which wrapped last Monday with three consecutive performances at the Hollywood Bowl in Los Angeles. He also has two scheduled shows in New York City at the beginning of November.
He was forced to cancel a Sacramento date last-minute back in August due to an undisclosed illness.
Tom Petty and the Heartbreakers became a household name in the mid '70s when they burst onto the music scene. The band is known for hits such as "American Girl," "Free Fallin'," "I Won't Back Down" and "Stop Draggin' My Heart Around" with Stevie Nicks.
He was also a member of the late '80s supergroup the Traveling Wilburys with Bob Dylan, George Harrison, Roy Orbison and Jeff Lynne.
Petty has sold over 80 million records worldwide over the course of his decades-long career. He was honored for his achievements back in 2002 when he was inducted into the Rock and Roll Hall of Fame.