A forensics team works the scene Thursday, Nov. 8, 2018, in Thousand Oaks, Calif. where a gunman opened fire Wednesday inside a country dance bar crowded with hundreds of people on "college night," wounding 11 people including a deputy who rushed to the scene. Ventura County sheriff's spokesman says gunman is dead inside the bar.

THOUSAND OAKS, Calif. (AP) Using a smoke bomb and a handgun, a hooded gunman dressed all in black opened fire during "college night" at a country music bar in Southern California, killing 12 people and sending hundreds fleeing in terror, authorities said Thursday. The gunman was later found dead.

Authorities said the motive for the attack Wednesday night was under investigation.

Patrons screamed in fear, shouted "Get down!" and used barstools to smash second-floor windows and jump to safety as gunfire erupted at the Borderline Bar & Grill, a hangout popular with students from nearby California Lutheran University. The dead included 11 people inside the bar and a sheriff's sergeant who was the first officer inside the door, Ventura County Sheriff Geoff Dean said.

"It's a horrific scene in there," Dean said in the parking lot. "There's blood everywhere."

The killer a 28-year-old man deployed a smoke device and used a .45-caliber handgun, a law enforcement official told The Associated Press. The official was not authorized to discuss the investigation publicly and spoke on condition of anonymity.

It was the deadliest mass shooting in the U.S. since 17 students and teachers were killed at a Parkland, Florida, high school nine months ago. It also came less than two weeks after a gunman massacred 11 people at a synagogue in Pittsburgh. That, in turn, closely followed the series of pipe bombs mailed to critics of President Donald Trump.