SACRAMENTO, Calif. -- Airman 1st Class Spencer Stone, hailed as a hero for helping to tackle a gunman on a French train in August, was stabbed and seriously wounded outside a bar in his hometown early Thursday in what police said was an alcohol-related fight that had nothing to do with terrorism.

Stone, 23, was stabbed repeatedly in the upper body while out with four friends and was taken to UC Davis Medical Center, authorities said. He was expected to pull through.

CBS News has learned that Stone was in stable condition after surgery. According to a source, he has a collapsed left lung and was expected to remain in the hospital for two to four days.

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Thursday evening, police released a new video that they say they believe shows suspects fleeing the scene.

Update - video of suspects fleeing the scene: This investigation continues to be extremely active and ongoing. ... Posted by Sacramento Police Department on Thursday, October 8, 2015

During a news conference Thursday, hospital officials said Stone is in serious condition, but is expected to make full recovery. Hospital officials said he has three stab wounds to his torso. And he is currently heavily sedated but conscious.

Police said two assailants, described by Deputy Police Chief Ken Bernard as male Asian adults, fled in a car. No immediate arrests were made.

"This incident is not related to terrorism in any way," Bernard said. "We know it's not related to what occurred in France months ago."

Bernard said the stabbing was "related to a nightclub incident" involving Stone's crowd and another group of people. Bernard would not say what the fight was about and said there was no evidence Stone's assailants knew who he was.

Police released surveillance video of an altercation outside a bar that left Spencer Stone with multiple stab wounds on October 8, 2015, in Sacramento, California. CBS News

The deputy chief said he did not know whether Stone was drinking, but others in his group were.

A law enforcement official said when Stone's group left the bar he and the suspect got into an argument that led to his stabbing, CBS News senior investigative producer Pat Milton reports.

Neither Stone nor the people with him appear to know the suspect, the official said.

Stone was not armed, the official said.

In a statement, the hospital said Stone's family "appreciates the outpouring of love and support" and requests privacy.

Over the summer, Stone and two of his childhood friends from Sacramento, National Guardsman Alek Skarlatos and college student Anthony Sadler, were vacationing in Europe when they thwarted a terror attack on a Paris-bound passenger train by taking down Ayoub El-Khazzani, a man with ties to radical Islam. He had boarded the train with a Kalashnikov rifle, a pistol and a box cutter.

Stone, who is assigned to Travis Air Force Base in California, suffered a cut thumb and other injuries in stopping the gunman.

Skarlatos reacted to Stone's stabbing on Twitter.

Everybody send prayers out to the stone family today — alek skarlatos (@alekskarlatos) October 8, 2015

Stone is the second of the three Americans to be touched by violence since returning home. Last week, Skarlatos left rehearsals for TV's "Dancing With the Stars" to rush back to his hometown of Roseburg, Oregon, after a gunman killed nine people at the community college Skarlatos had attended.

President Obama met with the three Americans last month, praising them for their quick thinking and courage and calling them "the very best of America." They were also awarded France's highest honor by President Francois Hollande. The three appeared on late-night talk shows and received a parade in their hometown.

The stabbing happened in a busy area of central Sacramento ringed with bars and restaurants that is a popular nightlife destination for young adults and is generally considered safe.