An undated photo from a social media account of Omar Mateen, who police have identified as the gunman in the mass shooting at a gay nightclub in Orlando, Florida, on June 12, 2016. REUTERS

By now it is well know that the gunman in the shooting at Orlando, Florida's Pulse nightclub pledged allegiance to the Islamic State group during a 911 call in the heat of his standoff with police. However, Omar Mateen swore loyalty to the terror group (also known as ISIS or ISIL) hours before his deadly rampage, in an incendiary Facebook post.

FBI officials have confirmed that Mateen, the 29-year-old who killed 49 people and wounded more than 50 more when he opened fire in Pulse early Sunday morning, posted on Facebook just moments before, pledging allegiance to ISIS, ABC News reported. Mateen also called on Russia and the U.S. to stop bombing ISIS-controlled territory in the Middle East and warned of future attacks on U.S. soil.

“You kill innocent women and children by doing U.S. airstrikes ... now taste the Islamic state vengeance,” Mateen wrote. “In the next few days you will see attacks from the Islamic State in the U.S.A.”

The FBI also revealed that Mateen's internet search history in the weeks leading up the Pulse attack included searches for the Facebook accounts of the suspects in the December 2015 attack in San Bernardino, California, ISIS speeches, the gun store where he purchased the weapons he used in the Orlando shooting, and the Pulse nightclub itself.

The evidence should further complicate the debate over Mateen's motives in the shooting. While many, especially on the political right, have been quick to point to Mateen's ties to terrorism, many members of the LGBT community are considering the shooting as another example of violence toward lesbians, gays, bisexuals and transgender people in the U.S. Still others remain focused on the tragedy as another example of the country's potential need for stricter gun laws.

In the wake of the shooting, presumptive Republican presidential nominee Donald Trump has been adamant about the need to label this and similar acts of terror as being perpetrated by "radical Islam" and doubled down on his proposal to ban Muslims from entering the country. Meanwhile, President Barack Obama and presumptive Democratic nominee Hillary Clinton have both called the debate over an immigration ban and terminology a distraction that is at odds with American values and could damage the United States' ability to work with Muslim allies abroad.

"What exactly would using this language accomplish? What exactly would it change?" Obama asked during a speech Tuesday at the Treasury Department. "Calling a threat by a different name does not make it go away."