The suspect is 25-year-old Sammeon Waller. Detectives say he beat up his grandfather so badly, he's in a coma. The victim is 82-year-old Robert McPherson of Pomona.
"I'm just shocked about what happened," said Pablo Duarte, who lives next door to the victim.
Pomona police say they got a call on Friday from concerned neighbors, who said they hadn't seen McPherson in several days. Officers showed up at the victim's home on the 2900 block of Gayridge Street in Pomona to do a welfare check.
They found the back window of the home broken, and heard moaning sounds coming from inside. When they entered, they found McPherson lying on the ground, battered and bloody. He was rushed to a local hospital.
"This is a violent and senseless crime," said Deputy Police Chief Michael Olivieri.
Detectives say McPherson had a restraining order in place against his grandson because of past violence. Police say Waller was arrested for violating the terms of that restraining order in February. He was later released.
They say he was also arrested a few days prior to this attack, on suspicion of misdemeanor vandalism, for allegedly breaking the front window at McPherson's home. Again, he was released.
"I've been kind of waiting for it to happen - not the way it did, but I was waiting for something to happen," said a neighbor across the street, who tells Eyewitness News the victim and his grandson were fighting all the time. "He threatened that boy a lot, like he was going to beat him up and I told him to leave him alone, he's young and strong; (but) you're old like me."
"A real good friend; a real good neighbor," said Ruth Verdugo, who says she visited McPherson in the hospital on Monday. "He was asleep, and he was resting."
Pomona police believe Waller stole his grandfather's vehicle, a 2003 silver Honda Odyssey. It was impounded on Friday morning in front of a restaurant in Sacramento.
Police say Waller doesn't have any ties to the Sacramento area, and he might eventually return to Pomona.
Waller is a man of little means, who might be living on the streets, police said.
Anyone with information on his whereabouts is asked to call Pomona police at (909)620-2085 or provide an anonymous tip to Crime Stoppers at (800)222-8477.