Suspect Esteban Zaragoza did not enter a plea on Wednesday as he stood before a judge to be arraigned on murder charges.
Zaragoza is accused of shooting and injuring a couple and their infant as they left a baby shower Sunday morning in East Palo Alto. Zaragoza mistakenly believed the family was associated with a gang that had beaten him last month.
Three-month-old Isack Jesus Jimenez died from his injuries.
Jimenez's mother, Ivonne Garcia Lopez, was present at the Alameda County Courthouse on Wednesday and thanked the community for their support.
"We want to say thank you for everything," Lopez told reporters. "I appreciate all the help."
Zaragoza's mother was also present at her son's arraignment Wednesday, but chose to flee from photographers and reporters.
Alameda County Chief Deputy District Attorney Karen Guidotti says Zaragoza will be tried as an adult for the crime, which will come with multiple charges.
"This crime was particularly callous, heinous," Guidotti said. "The death of a three-month-old -- the most innocent of victims -- is unimaginable."
ABC7 News Legal Analyst Dean Johnson said Zaragoza faces life without the possibility of parole.
"Given the innocence of the victims -- the multiple victims, the allegations of gang involvement - were he an adult, this would almost surely be a death penalty case," Johnson said.
One of Zaragoza's neighbors say he is not a gang member, and she can't believe he would be capable of murder.
"It wasn't him," neighbor Angelica Tapia said. "I know it wasn't him."
Zaragoza will appear in court next Wednesday. Zaragoza will have an attorney with him and he will be expected to enter a plea at that time.
