A father and son were stabbed at a youth baseball game in Ventura, Southern California, on Sunday, police said.

The father was watching his 15-year-old son play, when at about 4 p.m. the man’s older son, who is 19, got into a fight with a group of men near the field in the 2000 block of Cameron Street, according to the Ventura Police Department.

The father went to assist his older son and both of them were stabbed, police said.

Blood stains on the steps of an elementary school next to the park show where police found a 21-year-old man with stab wounds to his upper body. Police believe he’s the attacker, and was likely stabbed by someone in his group.

"We don't know if it was by accident or some time during the altercation," Ventura Police Cmdr. Tom Higgins said.

The injuries of the men were described as serious.

The baseball game was canceled after the fight. Police were asking witnesses with photos or video to come forward.

"People are out watching a Sunday baseball game, it's unfortunate that it came to this," Higgins said.

Police said they took a person into custody a few blocks away.