Gary Kildall was so depressed he committed suicide, because Bill Gates (Microsoft) stole his OS and used it and his mothers position in IBM to undercut him, and he couldn't do anything about it.
PS:
I can write that Bill Gates and Microsoft stole it without fear of repercussions from either, because that's already been decided in a court of law decades ago.
Gary Kildall's lawyer later stated Gary Kildall lacked the tenacity Bill Gates had, because he didn't sue based on same lawyers legal advice, that software probably wasn't legally protected by copyright.
If you don't know, QDOS was copied from CP/M, and Microsoft bought QDOS and relabeled it MS-DOS, and sold it to IBM as PC-DOS. Main difference being that Microsoft removed the few safety features that were present in CP/M, causing decades of nightmares with bad security and viruses.
No it's not, I may remember that part wrong, it was speculated to be homicide, but his wife told he was very depressed about Microsoft using his own OS to win the contract with IBM.