A gunman opened fire on a line of people waiting to get into a Kansas City bar, killing one before he was gunned down by a security guard — a deadly end to a night of celebrations as the Chiefs advanced to the Super Bowl, authorities said.

The shooting happened around 11:30 p.m. outside the 9ine Ulta Lounge, where revelers gathered for an event that appeared to celebrate the Chiefs’ victory.

Authorities responding to the Noland Road bar, near US Highway 40, found a man and woman dead in the parking lot, police said on Twitter. The male victim is believed to have been the shooter.

As the investigation unfolded, police determined that at least 15 other victims arrived at local hospitals, at least three in critical condition.

Kansas City police Capt. David Jackson told reporters that police found a “chaotic scene, with several people running around” — and needed to call in additional officers from across the city for support.

The circumstances and motive behind the shooting are under investigation.

Police have not released the names of the two people killed, pending family notification.

“We don’t know if there was any specific person targeted or disturbance yet,” Jackson said. “We’re still investigating what led up to this. We’re not aware of a specific type of firearm or anything at this point.”

The lounge was holding a “Sold Out Sundays” event, according to an earlier post on its Facebook page. The Chiefs — featured on the event’s artwork — earned their place in the big game after defeating the Tennessee Titans, 35-24.

“It just put such a tragic end to such a wonderful day in Kansas City,” Jackson County Prosecutor Jean Peters Baker said at the scene. “It’s just hard to stand here and talk about this kind of tragedy on really one of the best days Kansas City has had in a long time.”