Sgt. Ron Helus, the Ventura County Sheriff's officer who was killed during the shooting at the Borderline Bar & Grill in Thousand Oaks, Calif., on Nov. 7, died due to friendly fire. New details released by investigators on Friday (Dec. 7) show that it was a bullet from the rifle of Helus' California Highway Patrol partner that killed him.

USA Today reports that Helus was also shot five times by the shooter in Borderline, Ian David Long, who killed 12 people and himself inside the bar that night. Helus and his partner were the first to respond to the scene. While it was friendly fire that caused Helus' death, Sheriff Bill Ayub reiterated during a press conference that authorities are considering Long responsible for all of the deaths in the tragedy.

The Borderline Bar & Grill was hosting "college country night" when Long walked in and began shooting on Nov. 7; some of those in attendance were also at the Route 91 Harvest Festival shooting in October 2017. Authorities have yet to determine Long's motive, though at a press conference in late November, they said that there is no evidence that he had been radicalized.

According to its website, the Borderline Bar & Grill is "Ventura County's Largest Country Dance Hall & Live Music Venue" and has been open since the late 1980s, when it was located in Malibu, Calif.; it moved to Thousand Oaks in 1993. Artists such as Lee BriceTyler Farr and more have performed at Borderline over the years. Brian Hynes, the venue's owner, has vowed to reopen after the investigation into the tragedy is complete.

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