A photo of Florida airport gunman Esteban Santiago appears to show him making a jihadist one-fingered salute while wearing a Mid-Eastern keffiyeh sometime prior to him carrying out the shooting massacre.

The 26-year-old Iraq war veteran was pictured in the photo gesturing with his index finger in a pose that has become notorious among supporters of the Islamic State.

Law enforcement officers are currently looking at whether Santiago had any links to ISIS or if he was mentally disturbed as part of their investigation into the deaths of five people in the baggage claim hall at Ft. Lauderdale airport on Friday.

Ft. Lauderdale airport gunman Esteban Santiago, 26, is pictured giving a one-fingered salute similar to a pose used by ISIS jihadists

FBI officials said late on Friday night they had not ruled out terrorism and were investigating all angles as they try to determine a motive for the shooting spree.

It was not immediately clear where or when the photo of Santiago was taken in which he appears to be making the jihadist salute.

The traditional Islamic gesture - which refers to the tawhid or 'the belief in the oneness of God' - has been widely adopted by Islamic State supporters.

Boston bomber Dzhokhar Tsarnaev posed in a similar stance in front of an Islamic flag in his bedroom.

Boston bomber Dzhokhar Tsarnaev posed in a similar stance in front of an Islamic flag in his bedroom

The traditional Islamic gesture - which refers to the tawhid or 'the belief in the oneness of God' - has been widely adopted by Islamic State supporters

Australian jihadi Khaled Sharrouf has also been pictured doing the one-fingered salute

Santiago was hospitalized for mental health treatment in November last year after he voluntarily walked into an FBI office in Anchorage, Alaska where he lives claiming the government was controlling his mind and forcing him to watch videos for ISIS.

A law enforcement official said the FBI interviewed him and then called the police, who took him for a mental health evaluation.

The FBI revealed on Friday that Santiago stated he did not want to harm anyone, but authorities were concerned by his erratic behavior.

They said they closed their assessment of him once he was admitted for treatment.

Santiago, who was part of the Army National Guard from 2007-2016, was deployed to Iraq in 2010. He spent a year there with the 130th Engineer Battalion.

Law enforcement officers are currently investigating whether Santiago, who served in Iraq, had any links to ISIS or if he was mentally disturbed

A firearm (believed to be pictured) was Santiago's only piece of checked luggage when he flew from Alaska to Florida on Delta via Minneapolis on Friday