Trump condolences Thousand Oaks: “fully briefed on the terrible shooting”.
Mr Trump said on Twitter that he has been “fully briefed on the terrible shooting”.
He praised law enforcement, saying “Great bravery shown by police” and said “God bless all of the victims and families of the victims”.
A gunman opened fire on a crowd at a country dance bar holding a weekly “college night” on Wednesday night.
The mass shooting killed 12 people and sent hundreds fleeing in terror.
The gunman was later found dead at the scene.
Law enforcement said the dead from the shooting included 11 people inside the bar and a sheriff’s sergeant who was the first officer inside the door.
Latest: Thirteen people have died, including a sheriff’s sergeant and the gunman, after a shooting inside a crowded Southern California bar.
Ventura County Sheriff Geoff Dean said sheriff’s Sergeant Ron Helus responded to the scene and was shot after he entered the building.
He died at a hospital early on Thursday but authorities did not say how the gunman died.
Mr Dean said around 10 other people were shot and wounded.
Ventura County Sheriff’s Office Captain Garo Kuredjian said the first reports of shots fired came around 11.20pm local time at the Borderline Bar & Grill in Thousand Oaks, which is about 40 miles west of Los Angeles.
The bar’s website said it hosts College Country Night every Wednesday.
The gunman who injured 11 people inside a Southern California bar is dead, Ventura County Sheriff’s Office Sergeant Eric Buschow has said.
A deputy who responded to the incident was shot and taken to a hospital while no other information on the other victims was immediately known.
The Borderline Bar & Grill in Thousand Oaks, which is about 40 miles west of Los Angeles.
The bar’s website said it hosts College Country Night every Wednesday and police said hundreds were inside when the shooting occurred.