FORT PIERCE , Fla., Sept. 12 (UPI) -- A fire early Monday at a Fort Pierce, Fla., mosque where Orlando massacre shooter Omar Mateen prayed, was caused by arson, investigators said.
"Evidence has revealed that this fire was set intentionally," St. Lucie County Sheriff's Major David Thompson said, citing a surveillance video indicating a person approached the Islamic Center of Fort Pierce immediately prior to a 911 call at 12:31 a.m. Monday that the mosque was on fire.
"Immediately after the individual approached, a flash occurred and the individual fled the area," Thompson added.
No injuries were reported.
Local authorizes and the Florida State Marshal's Office are investigating the fire. Thompson said the FBI and the Federal Bureau of Alcohol, Tobacco and Firearms will be asked to join the investigation.
Islamic Center leaders said the mosque had received threats after it was revealed Mateen, who shot 49 people to death at Orlando's Pulse nightclub in June, was known to worship there. Security had been increased, they said.
Mateen, who lived in Fort Pierce, was killed in a shootout with police.
The fire was discovered immediately after the 15th anniversary of the September 11, 2001, attacks.
"We all know the implications of the date and the time of year that this is, the 9/11 anniversary. Is that related? I would not want to speculate but certainly that is in the back of our minds," Thompson said. "This is a terrible tragedy, not only for the Islamic Center, but for our community."
The incident comes at the start of Eid al-Adha, an annual four-day Muslim holiday.