Harlan Thrombey

A wealthy mystery fiction author and the patriarch of the Thrombey family, whose mysterious death sets the plot in motion.

Death
Due to the mix-up, Harlan believed he had less than ten minutes to live, and that the Slayer rule would therefore disqualify Marta from his inheritance. With this in mind, he chose to end his own life, in order to protect Marta and her family. Harlan stopped Marta from calling an ambulance, and gave her a solid (albeit complicated) alibi which would allow her to avoid any suspicion regarding his death.

At the last moment, Marta turned around, perhaps hoping she could change Harlan's mind, but arrives just in time to see Harlan slit his own throat.

Post-Mortem
Harlan's body was discovered by Fran the next morning.

Personality
Harlan's big flaw is his flair for the dramatic. He knocks his own family out of his will but its mainly so they can build something for themselves rather than mooch off his own success. Even though Harlan comes across as a well-intentioned and charismatic person, he didn't think too clearly of the consequences that could affect Marta after he recklessly committed his own murder.