An arsonist started a fire at around 12:30 a.m. Monday morning at the Islamic Center of Fort Pierce, the Florida mosque previously attended by Omar Mateen, the infamous Orlando shooter. No injuries were reported, but it's unclear how much damage was done. 

In a video posted by the St. Lucie County Sheriff's Office, Maj. David Thompson told reporters "evidence has revealed that this fire was set intentionally" but that he doesn't "want to speculate on a motive." Thompson described the fire as a "horrible tragedy not only for the Islamic center but for our community."

On its official Facbeook page, the St. Lucie County Sheriff's Office said it will soon be releasing video that shows someone approaching the side of the building "just moments before a flash is seen and the fire starts." While noting that the investigation is "at a very early stage," the department said, "A fire at any place of worship is alarming, regardless of the circumstances."

The arson is almost certainly a hate crime: It happened around the first day of Eid al-Adha, one of the most important Muslim holidays, around the three-month anniversary of the shooting at Pulse nightclub in Orlando, when Omar Mateen killed 49 people, and the day after the 15th anniversary of 9/11.

The Islamic Center of Fort Pierce had planned an Eid prayer Monday morning, but because of the arson, worshippers were instructed to go to another mosque nearby.

Omar Mateen occasionally attended the Islamic Center of Fort Pierce since 2003. Along with his father and young son, Mateen's three sisters were active volunteers at the mosque, according to The Washington Post. Just two days before carrying out the deadliest mass shooting in American history, Mateen prayed at the mosque with his son.

Moner Mohammad Abusalha, the first American to carry out a suicide bombing in Syria, also occasionally worshipped at the mosque before he flew to Syria in 2014. However, the FBI found no "ties of any consequence" between the two men.

The national spokesperson for the Council on American-Islamic Relations, Ibrahim Hooper, said the "unprecedented rise in bigotry in our society" is becoming "a great concern to the American Muslim community."

The Islamic Center of Fort Pierce has dealt with Islamophobia before. Back in July, a few weeks after the Orlando shooting, a Muslim man outside the mosque was assaulted by an intoxicated man who reportedly said, "You Muslims need to go back to where you came from." 

"Please keep us in your Du'as [an invocation or act of supplication] and prayers," the mosque wrote on Facebook.