1-year-old girl accidentally shot and killed by 3-year-old sibling, authorities say

A 1-year-old girl was accidentally shot and killed Monday by her 3-year-old sibling, who had gained access to an unsecured handgun, authorities said.

The San Diego County Sheriff's Department said deputies responded to the shooting at a home in Fallbrook, California, on Monday morning.

The 1-year-old suffered a head injury in the shooting and was transported to a local hospital, where she was pronounced dead at about 8:30 a.m. Monday, the department said. The child's name has not been released at this time "out of respect for the family and the fact she is a juvenile," the department said.

"Sheriff's Homicide investigators are working to gather more information to determine the circumstances of the death," the San Diego County Sheriff's Department said in a statement. "There are no outstanding suspects and there is no threat to the community."

The investigation is ongoing. The San Diego County District Attorney's Office has been notified and will be updated with the investigators' findings, the sheriff's department said.

The local medical examiner's office will also conduct an autopsy to determine the cause and manner of death. A sheriff's department spokesperson told ABC News on Tuesday that they will release more information on the case following the autopsy.

As of July 15, so far this year there have been at least 221 unintentional shootings by children in the U.S., resulting in 78 deaths and 151 injuries, according to gun violence prevention organization Everytown for Gun Safety.