SACRAMENTO — Authorities were grappling Monday to determine what drove a young father to fatally beat his 2-year-old son on a farm road outside Turlock before a police officer arrived and shot the man to death.
One motorist who tried but failed to wrestle Sergio Casian Aguilar, 27, away from the child said the assailant was forceful and hollow-eyed, muttering that there were "demons" in the boy, according to a local newspaper account.
At one point, witnesses saw Aguilar, who had no criminal record or history of mental illness, bash the toddler to the pavement like a doll, and then stomp on him, authorities said.
The scene unfolded late Saturday on a narrow, cracked two-lane strip of pavement surrounded by farms southwest of Turlock, about 60 miles south of Sacramento.
Passing motorists called the Stanislaus County Sheriff's Department to report the beating shortly after 10 p.m.
Several tried in vain to stop the assault, said Deputy Royjindar Singh, a sheriff's spokesman.
"They were trying to pull him off the little boy, but he would push them away and go back to what he was doing."
One motorist, Dan Robinson, 52, a volunteer fire chief in nearby Crows Landing, was among those who tried to intercede.
Robinson did not return phone calls from The Times but told the Modesto Bee that at first he passed the scene and thought an animal had been hit.
But when he backed up to offer help, he realized that the man was beating a small child. He confronted Aguilar, who lunged at him, grabbing at a pen in his pocket, then pushed him away.
"There was a total hollowness in his eyes, like I could see right through to the back of his head," Robinson told the newspaper.
A sheriff's helicopter arrived six minutes after the initial 911 calls, with Modesto Police Officer Jerry Raymar aboard, authorities said.
The helicopter focused its spotlight on the scene below, where Aguilar continued to beat the child.
The helicopter landed in a cow pasture. The officer jumped out, drew his pistol and ordered Aguilar to stop what he was doing, authorities said.
When he continued to stomp on the child, the officer opened fire.
Paramedics rushed the child to a Turlock medical center, but he was dead on arrival, authorities said.
The boy was so badly beaten that he could not be identified by sight, Singh said, and authorities are conducting DNA tests to confirm his identity. Results are expected in three days. Toxicology tests on Aguilar are also being run to determine if the father might have been under the influence of alcohol or drugs.
Aguilar was separated from the boy's mother. Detectives have yet to determine a motive in the killing. "They're not sure we'll ever really know why he did this," Singh said.