Stephen Chamberlain, once Mike Lynch’s co-defendant in a US fraud trial, has died after being hit by a car while out running in Cambridgeshire, his lawyer has said.

Chamberlain, the former vice-president of finance at British software firm Autonomy, was hit on Saturday morning and had been placed on life support, Reuters reported.

On Monday Lynch was reported missing after a superyacht sank off the coast of Sicily during a violent storm. One man, understood to be the vessel’s chef, was confirmed dead and six others, including Lynch and his 18-year-old daughter, Hannah, remained unaccounted for on Monday evening.

Chamberlain died after being “fatally struck” by a car while out running, his lawyer Gary Lincenberg said.

Lincenberg added: “He was a courageous man with unparalleled integrity, and we deeply miss him. He fought successfully to clear his good name, which lives on through his wonderful family.”

Cambridgeshire police had appealed for witnesses after the collision in Newmarket Road in the village of Stretham. The force had said a man in his 50s had been taken to hospital with serious injuries.

Chamberlain and Lynch were co-defendants in a fraud trial over the sale of Autonomy to Hewlett-Packard in 2011 for $11bn (£7bn).

The pair faced the same charges of fraud and conspiracy for allegedly scheming to inflate the company’s value before it was sold.

Both men were acquitted of all 15 charges by a jury in San Francisco in June.

After leaving Autonomy in 2012, Chamberlain worked as chief operating officer for cybersecurity firm Darktrace and volunteered as a finance director for League One football club Cambridge United.