The night is popular among the area's local university students/ EPA
At least 12 people have been killed, including a police officer, at a bar in Thousand Oaks, California.
Police say the shooting began at 23:20 local time on Wednesday at the Borderline Bar and Grill about 40 miles (65km) north-west of Los Angeles, according to BBC report.
At least another 10 were injured in the attack. Officials say the suspect was found dead inside and have not yet identified him. They do not yet know his motive for the shooting.
At least 200 people were reportedly inside the bar attending a college country music night at the time.
"When deputies arrived they heard shots being fired, it was an active shooter situation," Ventura County Sheriff's office spokesman Eric Buschow said earlier.
The police officer who was killed has been named as Ventura Sheriff's Sergeant Ron Helus - a 29-year force veteran an father-of-one who was due to retire next year. He was shot several times and later declared dead at a local hospital.