The boy, whose name was not released, allegedly had been beaten up by Sureno gang member in Redwood City on May 31, and believed he could exact revenge Sunday when he thought he saw a gang member getting into a car in East Palo Alto, The San Francisco Chronicle reported Tuesday.
The car, however, was carrying a four-member family leaving a baby shower that had no connection to the earlier beating, East Palo Alto acting police Capt. Jeff Liu said.
The suspect and another boy, 16, came up to the car and repeatedly fired into the front and back seats, killing 3-month-old Izak Jesus Garcia-Lopez and wounding his parents, Ivonne Garcia-Lopez and Oscar Jimenez, 22, police said.
The mother's leg stopped a bullet that may have otherwise hit Isaiah, her 4-year-old son, the newspaper reported.
"He was such a precious angel. He is my everything. I was making my own little family and we were happy, and this person came into my life and destroyed it. They killed my baby and they killed part of my soul, too," the mother said.
Jimenez is hospitalized with a shoulder wound, but is expected to recover.
The two boys were arrested at the 17-year-old's East Palo Alto home on suspicion of weapons violations. Police discovered three weapons on the premises, including a gun believed to have been used in the car attack, Liu said.
The older boy was charged with murder after he "provided statements implicating himself," Liu said.
Police believe the younger boy was involved, but he has not yet been charged.