Jonathan Boies, a son of renowned trial lawyer David Boies and one of the first hires at the law firm that became Boies Schiller Flexner, died on Feb. 22 of complications related to a vascular brain condition.

A source close to the firm and David Boies confirmed the death, saying it came unexpectedly in Aventura, Florida while Jonathan Boies was in the state for a family birthday celebration. The cause was a rare condition called arteriovenous malformation, which impacts blood vessels that connect to arteries and veins in the brain.