Officers responded to reports of at toddler who was shot at a home in the 7500 block of Kentwood Court just before 5 p.m., according to the Gilroy Police Department.
Paramedics immediately began treating the boy for life-threatening injuries, but he was pronounced dead on the way to a hospital, police said.
A preliminary investigation revealed that the boy had been shot with a handgun, police said. The boy was in his own home and family members were home at the time.
An investigation into the incident was under way by Gilroy police, the Santa Clara County District Attorney's Office and the Santa Clara County medical examiner's office.
The investigation will involve how firearms were stored at the residence, police said.