Cpl Kevin Cueto's father Phil has been training with CrossFit SV since it started.
The Department of Defense says a 23-year-old Marine corporal from San Jose was killed in Afghanistan when an improvised explosive device went off.
Kevin Cueto died on Tuesday while supporting combat operations in the country's southwestern province of Helmand.
Officials say Cueto, a rifleman, was on his second combat deployment. He served in Iraq in 2009.
He was a recipient of the Purple Heart and the Navy and Marine Corps Achievement Medal.
He was assigned to a Marine unit based out of California's San Bernardino County.
Our CFSV prayers go out to the Cueto family.