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Prince was working on a "few key projects," including new music, before his illness and death, the first source told E! News.

"Prince was extremely happy and upbeat about life and his music a few weeks ago," the source added. "His energy was high and he was feeling healthy."

Prince appeared to be in great spirits when he attended a Golden State Warriors vs. Oklahoma City Thunder NBA game in March. He was filmed walking courtside with a cane, which he has sported for many years, reportedly due to hip problems.

Prince also had epilepsy.

"I've never spoken about this before but I was born epileptic and I used to have seizures when I was young and my mother and father didn't know what to do or how to handle it, but they did the best they could with what little they had," he said on the PBS show Tavis Smiley in 2009. "the My mother told me one day, I walked in to her, and said, 'Mom, I'm not gonna be sick anymore' and she said, 'Why?' and I said, 'Because an angel told me so.'"

"Now, I don't remember saying it, that's just what she told me," he said. "And from that point on I've been having to deal with a lot of things—getting teased a lot in school and you know, early in my career, I tried to compensate for that by being as flashy as I could and as noisy as I could."

In addition to his music, Prince was known for his elaborate, eclectic stage styles.