It happened at a bar in the city of Thousand Oaks

Police in the US State of California say 12 people have been killed in a shooting at a bar in the city of Thousand Oaks.

Among them is a police officer who was planning to retire next year.

Sergeant Ron Helus  worked on the force for nearly three decades.

The gunfire broke out during a country music night in The Borderline Bar and Grill at around 11:20 local time last night.

It was packed with hundreds of people when the gunman attacked.

Police say they've identified the suspected shooter as 28-year-old Ian David Long, a former Marine.

Authorities believe he killed himself after opening fire