Orlando killer's inflammatory comments come to light

Last Updated Jun 16, 2016 2:44 PM EDT

With the help of a grand jury, investigators are stepping up their search for evidence showing that Orlando shooter Omar Mateen's wife, Noor Salman, may have played a role in the planning of the attack, reports CBS News correspondent Jeff Pegues.

Law enforcement sources said she purchased ammunition with her husband, and they believe she drove with him as he cased the Pulse nightclub. If it is determined that she had prior knowledge of the attack, she could face criminal charges.

CBS News has learned that other family members are being looked at by investigators as well.

On the heels of the mass shooting that left claimed the lives of 49 victims, the Department of Homeland Security has extended a bulletin it released late last year, saying it is concerned about homegrown violent extremists who could strike with little or no notice.

The bulletin, first issued late last year, warns that "terrorists will consider a diverse and wide selection of targets for attacks" and "inspire individuals to violence."

Investigators believe Mateen was radicalized in recent years, and they point to the Facebook message the killer posted before the massacre as evidence.

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

What did wife of Orlando gunman know before shooting?

The message was a precursor for what was to come inside Pulse nightclub.

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

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 Muslim went out with Mateen. 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.

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

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 continues to dig into Mateen's background. What they are uncovering is the 29-year-old's erratic behavior.

The St. Lucie County sheriff's office has confirmed that it wanted Mateen transferred out of a Florida courthouse in 2013 after they said he made inflammatory remarks about women and Jews and then praised the Fort Hood shooter.

Mateen worked for G4S as an armed security guard. They said he had a Florida security officer license which was renewed four times. Each renewal required a criminal background and FBI check. Records show he'd had extensive firearms training and was a good shot.

In a 2012 documentary about the BP oil spill, he was seen telling producers that he was skeptical of the clean-up effort.

"They're like hoping for more oil to come out and more people to complain so they'll have jobs," Mateen said on camera.

"He was just a very agitated type of individual," Mateen's former co-worker David Gilroy said.

Gilroy quit when he said he felt harassed by Mateen.

"He was on the verge of violence all the time," Gilroy said.

President Obama and Vice President Biden will travel to Orlando Thursday to meet with families of those killed at the nightclub, as well as first responders.