Richard Simmons, popular 1970s and 80s fitness guru, has died, law enforcement sources confirmed to NBC News. He was 76. Simmons was found unresponsive in his home in the Hollywood Hills neighborhood of Los Angeles the morning of July 13, according to two law enforcement sources.

L.A. Fire and Los Angeles Police Department officials responded to a call at 1 p.

m. ET, according to officials. Simmons was pronounced dead at the scene.

The cause of death is pending. Simmons' 76th birthday was just a day earlier on July 12, when he thanked fans and loved ones on for the celebratory wishes. "Thank you.

..I never got so many messages about my birthday in my life! I am sitting here writing emails.

Have a most beautiful rest of your Friday," he wrote in a post, before signing off, "Love, Richard." Reminiscing on his birthday, Simmons told in a recent interview that this year, he’s “grateful that I’m here, that I am alive for another day.” In March, Simmons shared to that he had been the most common form of skin cancer.

"There was this strange looking bump under my right eye. I had a tube of neosporin which I would put on I the morning and the evening..

..it was still there.

It was time to call my dermatologist," he said of his skin cancer discovery in the post. Simmons continued, "I sat in his chair and he looked at it through a magnifying mirror. He told me he would have to scrape it and put it under the microscope.

Now I am getting a little bit nervous. He comes back about 20 m.