US news outlets reported that he was stabbed four times in the chest, and that he suffered a wound to the heart and the lung.
Although, the US airman is in a stable condition and his injuries are non-life threatening, initial reports suggested that the attack was so violent that police began treating the case as a homicide when they arrived on the scene.
Police said in statement: "It is believed that the victim was out with a group of friends when a physical altercation led to the victim being stabbed multiple times in his upper body.
"Detectives were called to the scene to assist with the investigation and the victim is currently being treated for what appears to be non-life threatening injuries."
Police added: "The assault incident is not related to a terrorist act. Assault occurred near a bar, alcohol is believed to be a factor."
Airforce spokesman Lt. Col. Christopher Karns said Stone was being treated in a hospital in the Sacramento area.
Stone, 23, and two of his childhood friends from Sacramento, National Guardsman Alek Skarlatos and college student Anthony Sadler, were vacationing in Europe over the summer when they took down a gunman on a Paris-bound passenger train, receiving sudden celebrity and worldwide accolades.
A British businessman and a French-American also have been praised for their efforts to stop the gunman.
President Barack 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 hometown parade in their honor.
Stone suffered a cut thumb and other injuries in stopping the train attack. He is assigned to Travis Air Force Base in California.

