CCTV has revealed that Spencer Stone was stabbed from behind during a brawl near a bar in Sacramento.
First Class Airman Stone, 23, was stabbed four times after an altercation in a nightclub led to a confrontation in a street.
The footage appears to show Stone knocking a man to the ground before he is stabbed from behind.
Deputy Chief Ken Bernard of Sacramento Police said two suspects, described as Asian males in white T-shirts and blue jeans, fled the scene in a late-model Toyota Camry, NBC News reported.
The incident has not been treated as related to terrorism or Stone's involvement in thwarting an attack by gunman Ayoub El Khazzani on a train to Paris in August.
Michel Platini will step aside from his official duties after he was suspended for 90 days by FIFA's ethics committee on Thursday, UEFA confirmed.
In a statement, European football's governing body said: "Michel Platini is currently suspended and will therefore not perform his officials duties for the time being. As such he did not attend the meeting of the UEFA executive committee today and has cancelled several official trips.
"UEFA is fully aware of its responsibilities under the relevant provisions of the statutes."
Michel Platini has promised to "staunchly" defend himself against claims of wrongdoing after he was suspended by Fifa for 90 days.
The 60-year-old president of Uefa branded the allegations "farcical" and "astonishingly vague", vowing to ensure that his "good faith prevails".
However, in his statement Platini conceded he did not believe the actions by Fifa's ethics committee to be politically motivated because of his candidature for the Fifa presidency.
Despite the farcical nature of these events, I refuse to believe that this is a political decision taken in haste in order to taint a lifelong devotee of the game or crush my candidacy for the FIFA presidency.
I want everyone to know my state of mind: more than a sense of injustice or a desire for revenge, I am driven by a profound feeling of staunch defiance. I am more determined than ever to defend myself before the relevant judicial bodies.
I want to reiterate in the strongest possible terms that I will devote myself to ensuring that my good faith prevails.
Greg Dyke has expressed sadness that corruption has dominated football in the wake of Sepp Blatter's suspension from Fifa.
"I think it was inevitable that Sepp Blatter would be suspended for something but It's a sad day for football that corruption dominates the headlines yet again," Greg Dyke told ITV News.
Dyke added he thought there would be many people pleased at the "final demise" of Blatter and thought it was "pretty obvious" that he would not survive the scandal.
"From the moment when the FBI got involved and knocked on all those doors, I think it was the beginning of the end for Sepp Blatter."
Regarding Michel Platini, Dyke said that if there was any evidence that showed Uefa's boss had committed wrongdoing, then the FA would not support his candidature for Fifa president.
European football's governing body UEFA has expressed its "full confidence" in Michael Platini.
UEFA's president has been suspended from all footballing activities for 90 days by Fifa as investigations into financial wrongdoings continue.
However, in a statement UEFA said it "saw no reason" for Platini to be replaced at the top of the Association and would "stand fully" beghind him.
In light of the events occurring today regarding UEFA President Michel Platini, the UEFA Executive Committee has taken the following decisions on 8 October.
An Emergency meeting of the UEFA Executive Committee will be convened in Nyon on Thursday, 15 October; in addition, all 54 member associations of UEFA will meet at UEFA Headquarters on the same day.
The UEFA Executive Committee saw no need, at this moment in time, to invoke Article 29(5) of the UEFA Statutes, pursuant to which the highest-ranking Vice-President of UEFA may step in to assume the powers and duties of the President in his absence.
This is because the UEFA Executive Committee is aware that the UEFA President will immediately take all necessary steps to appeal the decision of the FIFA Ethics Committee to clear his name. Furthermore, the UEFA Executive Committee stated that there must be a very rapid final decision on this matter before the relevant bodies, in the interests of both justice and football.
Finally, the UEFA Executive Committee expressed its full confidence in UEFA President, Michel Platini, and stands fully behind him.
The scandal enveloping world football's governing body dates back nearly five years.Read the full story ›
Police closed a two-block area following the stabbing of Spencer Stone in 21st Street and K Street in Sacramento near some popular bars.
Stone was with a group of friends when a "physical altercation" occurred and he was stabbed in the chest four times.
No arrests have been made but police have said the attack is not related to a terrorist act and that alcohol was a factor in the incident.
Police have confirmed that the stabbing of French train hero Spencer Stone was not "related to a terrorist act".
A statement said that the assault took place near a bar and "alcohol is believed to be a factor".
Update: The assault incident is not related to a terrorist act. Assault occurred near a bar, alcohol is believed to be a factor.
Police say Spencer Stone was stabbed when involved in a 'physical altercation' while out with a group of friends.
In a Facebook post, Sacramento PD said:
On Thursday, October 8, 2015, at 12:46 a.m., the Sacramento Police Department received a call from a passerby that a subject had been stabbed in the area of 21st Street and K Street.
The victim, a man in his 20s, was located on scene and transported to an area hospital by fire personnel.
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.
The Sacramento Police Department respects the identity of all crime victims and appreciates your patience as we work to provide you with further details.
No arrests have been made at this time.
Soldier Alek Skarlatos who helped Spencer Stone foil the French train terror attack, has tweeted his support after the airman was reportedly stabbed.
Skalatos, 22, who overpowered a terror suspect on a high-speed train in France alongside fellow serviceman Stone, urged people to "send prayers" to his family.
Everybody send prayers out to the stone family today