Authorities said Friday they are investigating whether the man accused of torching a Florida mosque sometimes attended by the Orlando nightclub shooter was part of a conspiracy.

Lt. Adam Goodner of the St. Lucie County Sheriff's Office said in an email to The Associated Press that detectives are investigating who Joseph Schreiber, 32, spoke to on his cellphone moments before the fire was set Sunday night at the Islamic Center of Fort Pierce. Detectives said in their arrest affidavit that surveillance cameras at the mosque, which was attended by Omar Mateen, caught the arsonist talking to someone.

"Those avenues are being investigated. This is still very much an active investigation," Goodner wrote. He declined to give further details.

Mateen was killed by police after opening fire at the Pulse nightclub on June 12 in a rampage that left 49 victims dead and 53 wounded, making it the worst mass shooting in modern U.S. history. Mateen professed allegiance to the Islamic State group. His father is among roughly 100 people who regularly attend the mosque.

Schreiber told detectives he was embarrassed by his actions and never intended to hurt anyone, according to the affidavit. No one was injured in the fire, which burned a 10-by-10-foot hole in the roof at the back of the mosque's main building and blackened its eaves with soot.

Ralph Alfonso is a former inmate who says he served time with Schreiber at Lawtey Correctional Institution, a faith-based prison where both were incarcerated earlier this decade. In a telephone interview Thursday night, Alfonso described Schreiber as being a "couple cans short of a six-pack" and said he doesn't think Schreiber is intellectually capable of setting the blaze without coaching.

He said Schreiber joined a Messianic Jewish group he led because Schreiber was looking for a place to fit in. Messianic Jews follow Jewish law and the Torah but also believe that Jesus Christ is the Messiah. He said Schreiber sometimes would say something against Muslims, but "we would tell him that's not what we believe, that it is not godly."

"He wasn't a bad guy, he was just an oddball that no one really wanted to hang around with," said Alfonso, who was released in May after serving 17 years for aggravated assault on a law enforcement officer. He now works as an electrician. He said his group tried to shield Schreiber from bullying.

Schreiber was previously sentenced twice to state prison for theft, according to records from the Florida Department of Corrections. The records show he served his first sentence from March 2008 to July 2009 and his second from June 2010 to August 2014.

The TCPalm newspaper reported Friday that Schreiber has an extensive local arrest record dating to 2003 for crimes such as shoplifting, larceny, punching his father in the eye and threatening department store employees with a knife after they caught him trying to steal some shirts. The paper says a Fort Pierce woman accused Schreiber of stalking her earlier this year and requested a restraining order.