David Bowie's final email to a collaborator was a heartbreaking 'goodbye'

David Bowie's death Sunday came as a shock even though Bowie was 69 and suffering from liver cancer. That's because Bowie not only hid his illness from the public - he also kept working tirelessly.

Bowie's last album, "Blackstar," came out just last week, two days before Bowie's death, and it marked a whole new chapter in his music.

But behind the scenes, Bowie was quietly telling a different story. Brian Eno, a musician who was a frequent collaborator of Bowie's (helping usher in his Berlin era), has shared details about his correspondence with the singer and Bowie's emotional final email to him.

"David's death came as a complete surprise, as did nearly everything else about him. I feel a huge gap now," Eno said in a statement, according to the BBC. "We knew each other for over 40 years, in a friendship that was always tinged by echoes of Pete and Dud. Over the last few years - with him living in New York and me in London - our connection was by email. We signed off with invented names: some of his were mr showbiz, milton keynes, rhoda borrocks, and the duke of ear."

Eno added that the two had been talking about their last album together, "Outside," and how they "felt that it had fallen through the cracks" and wanted to revisit it.

The last cryptic reply from Bowie came just before his death. Eno says he knows now that it was Bowie's way of saying farewell:

"I received an email from him seven days ago. It was as funny as always, and as surreal, looping through word games and allusions and all the usual stuff we did. It ended with this sentence: 'Thank you for our good times, brian. they will never rot.' And it was signed 'Dawn.'

"I realise now he was saying goodbye."