06/15/2016 AT 01:40 PM EDT
Salman, 30, has reportedly said she pleaded with her 29-year-old husband not to do anything violent at Pulse after he assured her he was going to see friends on Saturday night,
NBC News reports.
Authorities say Mateen drove two hours from their home near Port St. Lucie to Orlando, and opened fire at the gay-friendly club early Sunday morning. Forty nine people were killed, with 53 wounded in what is now the worst mass shooting in modern U.S. history and the most deadly act of terrorism in America since the Sept. 11, 2001 attacks.
CBS News reports that according to law enforcement sources, Salman told authorities she believed Mateen might have been planning an attack at Pulse because she drove him to the club to scope it out and said she also went with him to buy ammunition and a holster.
Law enforcement sources have told Fox News that federal prosecutors have convened a grand jury to investigate Salman. Reuters also quotes law enforcement sources as saying Salman is the subject of an investigation. She is said to be cooperating with the FBI, and according to CBS has submitted to a polygraph.
Salman has not spoken publicly about her husband’s attacks and it is not known whether she has retained an attorney. She was pictured by local news station WSVN returning home on Tuesday.
Representatives for the U.S. Attorney’s Office for the Middle District of Florida and the FBI would not comment to PEOPLE on whether Salman is cooperating with investigators or whether a grand jury is being empaneled to investigate her.
Faces of Orlando: Heartbreaking Stories of Lives Lost and Heroic Actions in the June 12 Attack
— Brian Entin (@BrianEntin) June 14, 2016
Earlier this week, a federal law enforcement source told PEOPLE that Mateen recently scouted Walt Disney World as a potential target, visiting the resort in April with his wife. Salman told federal authorities on Sunday that her husband had more recently been “scouting Downtown Disney and Pulse [nightclub] for attacks.”
Unlike the four Disney World theme parks, Downtown Disney, which was recently renamed Disney Springs, doesn’t have security and bag check before entry.
Sitora Yusufiy, Mateen’s first wife, said during a press conference on Sunday that she believes Mateen suffered from mental illness.
“He was mentally unstable and mentally ill and he was obviously disturbed, deeply,” she said. “That’s when I started worrying about my safety and he was abusing me physically very often and not allowing me to speak to my family and he kept me hostage from them. And I tried to see good in him even then but my family was very tuned in to what I was going through and decided to visit me and rescue me out of that situation.”
The two were married for four months and divorced in 2011. Yusufiy says that she had not spoken to Mateen, whom she calls “bipolar,” or his family in several years.
Mateen had been investigated by the FBI twice before Sunday’s incident, but was cleared. During the shooting he called 911 and pledged allegiance to ISIS. The terrorist group has since claimed responsibility for the massacre. However, authorities are still investigating actual links between Mateen and ISIS.
Mateen’s says the shooter had previously shown hatred toward gay people.