From Twitter:

> After almost 4 years, I made the difficult decision to leave Facebook, and 12/30/20 was my last day at FB. I've had a great experience in a difficult, fun, fast-growing and impactful role at the company working with amazing people

From internet:

> At Facebook, RSUs are subject to a 4-year vesting schedule: 25% vests in the 1st year (5% every 2.4 months), then 25% in each of the 2nd, 3rd and 4th years (6.25% every 3 months)

I guess good for him to enjoy his wealth now. I wish him good health.