A callous thief assaulted a 91-year-old California widower with a rock while the man was visiting his wife’s grave, police said.

The unnamed victim was sitting on a lawn chair when he was attacked from behind around 10:45 a.m. on Sept. 14.

The attacker — who authorities described as possibly a Latino or Hispanic man between the ages of 35 and 50 with slicked-back, long, gray hair — robbed him, then escaped on a mountain bike.

“This is a completely and utterly unprovoked and ruthless assault on one of the most vulnerable members of our community,” Santa Clara Police Capt. Wahid Kazem told NBC Bay Area.

The victim was taken to the hospital and is now recovering at home, according to authorities.

A cyclist at the Mission City Memorial Park cemetery described the man as “a lovely gentleman who stays here for an hour or two visiting her” nearly every day, Denise Martin told CBS SF Bay Area.

Police are still searching for the attacker, who faces charges of felony assault, elderly abuse and robbery.