Story highlights "Last time I saw him, he was pretty sick," Gladys Knight says

Police believe the gunshot wound to Cornelius' head was self-inflicted, coroner says

Quincy Jones calls Cornelius a "visionary pioneer and a giant in our business"

Cornelius used his own money to launch "Soul Train" in 1970

Don Cornelius, the founder of the "Soul Train" television show, was found dead of an apparent self-inflicted gunshot wound to his head Wednesday, authorities said. He was 75.

Cornelius died of a gunshot wound at a house on Mulholland Drive, said Los Angeles police Officer Tenesha Dodine. Police responded to the call about 4 a.m. (7 a.m. ET), Dodine said.

Cornelius was pronounced dead at Cedars-Sinai Medical Center, according to Lt. Larry Dietz of the Los Angeles County Coroner's Office.

Los Angeles police investigators reported to the coroner that Cornelius died from a "self-inflicted gunshot wound to the head," coroner's Assistant Chief Ed Winter said. The coroner's office will perform an autopsy to confirm the cause of death.

Cornelius created a pilot for "Soul Train" using $400 of his own money, according to the website biography.com. The show was named after a promotional event he put together in 1969, the site said.

Photos: Don Cornelius through the years Photos: Don Cornelius through the years Don Cornelius through the years – "Soul Train" creator Don Cornelius, shown here on the set of the show in the '70s, died from a gunshot wound on Wednesday. He was 75. He was known for the catch phrase, "And as always in parting, we wish you love, peace and soul." Here's a look at Cornelius through the years. Hide Caption 1 of 9 Photos: Don Cornelius through the years 1970s – Cornelius hosted "Soul Train" from its 1971 premiere through the early '90s. Hide Caption 2 of 9 Photos: Don Cornelius through the years 1980s – Cornelius with Diana Ross on the show. Hide Caption 3 of 9 Photos: Don Cornelius through the years soul train don corneilus – Stevie Wonder apperas on the show. The elite of late-20th century black pop musicians, from Aretha Franklin, Smokey Robinson, James Brown, Teddy Pendergrass, Marvin Gaye, Al Green, Diana Ross and Gladys Knight, to the Jackson Five, O'Jays, Spinners, Gap Band and Commodores took live turns on the "Train" -- and frequently delivered some of their more potent televised performances. Hide Caption 4 of 9 Photos: Don Cornelius through the years 2001 – Shown here with the Rev. Jesse Jackson, from left, singer Smokey Robinson and TV personality Judge Greg Mathis, the "Soul Train" creator attended an event in December 2001. Hide Caption 5 of 9 Photos: Don Cornelius through the years 2004 – According to the website biography.com, Cornelius, shown here at a 2004 event, created a pilot for "Soul Train" using $400 of his own money. Hide Caption 6 of 9 Photos: Don Cornelius through the years 2005 – Cornelius posed with singer Usher at the 19th Annual Soul Train Music Awards in February 2005. Hide Caption 7 of 9 Photos: Don Cornelius through the years 2009 – Cornelius was a presenter at the BET Awards in June 2009. Hide Caption 8 of 9 Photos: Don Cornelius through the years 2011 – The Illinois native had a street named after him at Chicago's Millennium Park in September 2011. Hide Caption 9 of 9

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Gladys Knight, who performed on the pilot of the show more than four decades ago, said Cornelius "opened up so many avenues for African-American artists."

In an interview with CNN Wednesday, Knight said he appeared in ill health when she saw him recently.

"Last time I saw him, he was pretty sick," Knight said. "He had lost a lot of weight, but he still had that thing about him."

Singer Aretha Franklin called his death "so sad, stunning and downright shocking."

"Don Cornelius single-handedly brought about a melding and unity of brother and sisterhood among young adults worldwide and globally with the unforgettable creation of 'Soul Train,'" Franklin said.

Singer Smokey Robinson said it was "a musical tragedy."

"He brought exposure to black talent and a positive image to young black teenagers that had never been done before with his creation of 'Soul Train,'" Robinson said.

Music producer Quincy Jones expressed shock and deep sadness in a written statement to CNN.

"Don was a visionary pioneer and a giant in our business," Jones said. "Before MTV there was 'Soul Train,' that will be the great legacy of Don Cornelius. His contributions to television, music and our culture as a whole will never be matched."

The Rev. Al Sharpton, who said he appeared on "Soul Train" when he was 19 at the urging of his mentor James Brown, remained a friend to Cornelius for 38 years.

"He brought soul music and dance to the world in a way that it had never been shown and he was a cultural game changer on a global level," Sharpton said. "Had it not been for Don Cornelius we would not have ever transcended from the Chitlin circuit to become mainstream cultural trendsetters."

Former Motown Records Chairman Clarence Avant said the music industry "will forever owe a credit to him."

"'Soul Train' was the first and only television show to showcase and put a spotlight on black artists at a time when there were few African-Americans on television at all, and that was the great vision of Don," Avant said.

The program "is the longest running, first-run, nationally syndicated program in television history," according to the website of Soul Train Holdings. "During its 37-year run, the show featured such staples as the Soul Train line and performers as important and diverse as Al Green, Ike & Tina Turner, Marvin Gaye, The Jackson 5, Stevie Wonder, Elton John, Whitney Houston, David Bowie, Justin Timberlake, Janet Jackson and Beyonce."

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In 2008, MadVision Entertainment and Intermedia Partners acquired "the iconic franchise and catalog of more than 1,100 hours of archival footage from Don Cornelius Productions," the site said.

Cornelius once told Advertising Age he credited Dick Clark, host of "American Bandstand," for teaching him "almost all of what I learned about mounting and hosting a dance show," according to biography.com.

The show, which premiered in August 1970, showed teenagers dancing to the latest soul and R&B music as well as featuring guest performances.

Over the years, Cornelius presented many famous performers to "Soul Train's" audience, including Knight, Franklin, Smokey Robinson and Lou Rawls, biography.com said. However, the show did not always focus on soul and R&B music, featuring acts including David Bowie, Duran Duran and Robert Palmer, according to the site.

"But when audiences were watching the 'Soul Train' dancers for the next trend in fashion, true trendspotters knew to also watch Don Cornelius," according to an article posted on the Soul Train Holdings site. "... Has he ever looked like anything other than sharp? The answer to that question is no."

"Before Steve Harvey and his suits, Bobby Jones and Arsenio Hall, Don Cornelius was the original suit man," the article said. "For every outfit (he) deserves a standing ovation because he wore them well."

In September, a 40th anniversary "Soul Train" concert was held in Chicago's Millennium Park. Cornelius, a Chicago native, was honored at the event.

Cornelius began his career in broadcasting as part of WVON Radio in Chicago, which the Illinois General Assembly described in 2003 as "the first full-service, black-oriented music station in the city" as it congratulated the station on its 40th anniversary.

It was during his WVON days that he found himself at a show where the Jackson 5 performed in the mid-1960s, according to Time magazine.

When a young Michael Jackson opened his mouth to sing, Cornelius recalled being blown away, he told Time after Jackson's death in 2009.

"He's only 4 feet tall, and you're looking at a small person who can do anything he wanted to do onstage -- with his feet or his voice," Cornelius said. "To get to the level of people who can do that, you're talking about James Brown as a performer. You're talking about Aretha Franklin as a singer. Michael was like that as a kid. He did it all, within the framework of one package. Nobody else did that."