A 28-year-old Marine Corps veteran killed 12 people when he opened fire inside a busy bar in Thousand Oaks, California on Wednesday before killing himself and sending at least 15 others to the hospital with injuries.

The mass tragedy, which claimed police officer Sgt. Ron Helus and at least one survivor of the Las Vegas massacre among its victims, is the latest in 307 mass shootings that have occurred in the US so far in 2018.

Here's how the attack unfolded:

Wednesday night

A man police later identified as 28-year old Ian Long drove his mother's car from nearby suburb Newbury Park to the Borderline Bar and Grill,

The bar was holding its weekly college night.

The western-themed bar was reportedly popular among students from nearby universities including

Around 11:20 p.m. PT, Long approached the building and began shooting.

Long was reportedly dressed in all black and carrying a Glock 21 .45-caliber handgun as he approached the building.

After shooting a security guard outside, Long stepped inside to shoot several employees and opened fire inside the busy bar, shooting into a crowd of about 40 people on the dance floor.

Patrons reportedly hid under pool tables and used furniture to break windows and escape outside, some jumping from the second story.

Into Thursday morning

Video footage showed police officers standing outside the bar for up to an hour after their initial arrival. Other footage showed civilians carrying out injured people from the bar and tending to them.

Officers from the FBI Joint Terrorism Task Force and the Bureau of Alcohol, Tobacco, Firearms and Explosives were present at the scene.

The attack reportedly lasted just three minutes, but Long fired at police officers after they arrived.

Long was eventually found dead of a self-inflicted gunshot wound inside the bar's office.

In the hours after the attack, multiple reports revealed several people who survived the Las Vegas massacre in October 2017 were at Borderline that night.

At least one of the survivors from the Route 91 Harvest Festival massacre was shot Wednesday night.

Gunman

Out of more than 100 people who had been in the Borderline Bar & Grill, a witness estimated that dozens had survived the shooting in Las Vegas, though that was unconfirmed by authorities.

Thursday afternoon

Multiple reports began to reveal the victims' identities. CNN reported the known names so far of those confirmed dead included:

  • United Methodist Church Westlake Village.
  • a Marine Corps veteran.
  • California Lutheran University.
  • ctress Tamera Mowry-Housley

Thursday night

Approximately 2,000 people attended a vigil for the shooting's victims led by Thousand Oaks