Kevin Johnson

USA TODAY

WASHINGTON — The wife of the Orlando nightclub gunman feared that Omar Mateen was planning an attack and sought to dissuade him from going forward, a federal law enforcement official said Tuesday.

In interviews with federal investigators, Noor Salman also allegedly acknowledged driving Mateen to the Pulse nightclub at least once before her husband launched the assault, according to the official who was not authorized to speak publicly.

The attack, which now stands as the deadliest mass shooting in U.S. history, left 49 dead and 53 others wounded.

Salman allegedly told investigators that she drove Mateen to Pulse, a popular gay club in Orlando, about a week before Sunday's shooting, suggesting that the gunman had identified the target for some time before moving forward.

The development was first reported Tuesday by NBC News.

The federal official said authorities were seeking to substantiate the wife's account, along with other witness reports that Mateen had frequented the club often before returning with a rifle and handgun.

It is unclear whether Salman may face criminal charges, as authorities are seeking to determine whether she possessed enough detailed knowledge to alert authorities of Mateen's plot.

Among the possible charges available to federal authorities includes misprision of a felony, which was notably used in the prosecution of Michael Fortier, an associate of Oklahoma City bomber Timothy McVeigh. Fortier pleaded guilty to the offense and other weapons charges as part of deal in which he testified against McVeigh, offering crucial details about the bomber's prior planning leading up to the 1995 bombing that killed 168 people, then the deadliest act of terrorism on U.S. soil.

The FBI's focus on Salman and other family members is part of an extensive effort to construct a timeline of Mateen's activities in the weeks and days leading to Sunday's massacre.

Following a briefing by his National Security Council, President Obama Tuesday reasserted the government's belief that Mateen was not directed by a terror organization, even though the shooter expressed allegiance to the Islamic State during a standoff with police. Mateen also has professed solidarity with other extremist causes, some of them contradictory, creating a muddled portrait of the grievances that may have inspired him to lash out.

Obama rips Trump over proposed Muslim ban, 'radical Islam' rhetoric

Federal investigators believe Mateen had been in the Orlando area, on and off, for at least several days before the assault, the federal official said, adding that authorities were reviewing whether the gunman considered other targets, including the area's main tourist attraction, Disney World. It was entirely possible, however, that any association the gunman may have had with Disney was as a visitor.

Federal authorities also are reviewing past investigations in which Mateen surfaced as both a possible terrorist suspect and a suspected associate of a Vero Beach, Fla., man, who later died as a suicide bomber in Syria.

In each case, including a 10-month investigation into radical claims Mateen expressed to co-workers in 2013 in which he expressed interest in martyrdom, the matter was closed without charges.

FBI Director James Comey defended the bureau's work in those cases, saying that investigators found nothing to substantiate Mateen's rhetoric or an association with the suicide bomber Moner Abu-Salha.

'This is not a drill': Docs detail night in Orlando ER

Pulse patrons: Mateen hung out at the club 'for years'