A woman visiting her daughter’s apartment in Oceanside Tuesday night was shot by a neighbor who – while cleaning his gun – accidentally discharged a round into the floor that separates the units, striking the victim as she sat on the couch watching television.

The Oceanside Police Department (OPD) said the accidental shooting happened just before 11 p.m. at a small residential building on Bush Street, less than a half-mile from Interstate 5, in San Diego's North County.

Investigators said the neighbor, whose name was not released, had sat down to clean his 9mm Glock handgun when he accidentally discharged a chambered round into the floor of his apartment.

In the unit directly below was a woman from Huntington Beach, California, who was in town house sitting for her daughter. The bullet went through the floor and into the lower-level apartment, hitting the woman in the leg.

The neighbor who discharged the gun ran downstairs to help the victim and called 911. When officers and medics arrived, they found the neighbor rendering aid to the victim.

A crew with the Oceanside Fire Department rushed the shooting victim to a critical care unit. She was unconscious and barely breathing in the ambulance, the OPD said.

The woman’s wound is life-threatening; as of 12:15 p.m., her condition was unknown. Her name was not released.

No one else was hurt in the accidental shooting.

The OPD said detectives from the Crimes of Violence Unit are investigating. The neighbor who fired the gun is currently not in custody.