ORLANDO -- A former coworker of Orlando shooter Omar Mateen is speaking out following the massacre at Pulse nightclub that left 49 dead, and more than 50 injured.

Margaret Barone was Mateen's supervisor at the GNC in Jensen Beach, Florida, from February 2006 to November 2006.

On Sunday, Mateen carried out the deadliest terror attack on U.S. soil since 9/11.

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Barone told CBS News investigative producer Laura Strickler that Mateen was a good employee, and had no conflicts with other employees or customers, but she claimed he had started doing steroids.

Barone said that Mateen left the position at GNC to pursue law enforcement jobs. After he left, Barone said, Mateen started taking steroids and "he blew up" and became "huge."

Barone said during the alleged steroid use Mateen's arms went from 20 inches around to 40 inches around. She said he talked about doing steroids and was "doing too much," and continued to come into the store to buy supplements.

Barone told Strickler that another employee, who was also Muslim, went out with Mateen a number of times. The employee told Barone that Mateen drank so much he would often black out. This former employee said that Mateen did not treat girls well, and became "crazy and violent" when he drank.

Mateen ex-wife has accused him of beating her and being mentally ill.

The other employee also allegedly told Barone that she thought Mateen was gay.

Asked about his son's sexual orientation on Tuesday, Seddique Mir Mateen, Omar Mateen's father, said he did not believe his son was gay.

"To me, that is wrong," Seddique Mir Mateen told CBS News correspondent David Begnaud.

The elder Mateen said he learned of the speculation from news reports, but as far as he was concerned, "I didn't see any of it and I don't believe that was the case."

According to Barone, when Mateen worked for her, "He could do nothing right in his father's eyes."

Barone said she talked to his father many times and said his father would complain that Omar didn't have any direction or know what to do in life.

Barone told Strickler that while she allowed Mateen to do his prayers in the back of the store, she said he never said anything about 9/11 or sympathizing with radical Muslims.

The FBI is characterizing the shooting at Pulse as both a terrorist attack and a hate crime, CBS News' Paula Reid reported.

A source familiar with the investigation tells CBS News that Mateen referenced the Islamic State of Iraq and Syria (ISIS) in a Facebook message posted moments before the shooting.

"You kill innocent women and children by doing us airstrikes..now taste the Islamic state vengeance [sic]," Mateen wrote, according to the source.

"In the next few days you will see attacks from the Islamic State [ISIS] in the usa," the post said.