By Letitia Stein and Julia Edwards
ORLANDO, Fla./WASHINGTON (Reuters) - U.S. investigators have questioned the wife of the gunman who killed 49 people at a gay nightclub in Orlando, the FBI said on Wednesday, and a law enforcement source said she could face criminal charges if there is evidence of any wrongdoing.
Omar Mateen's wife, Noor Salman, knew of his plans for what became the deadliest mass shooting in modern U.S. history, said the law enforcement source, who has been briefed on the matter.
"With respect to the wife, I can tell you that is only one of many interviews that we have done and will continue to do in this investigation," FBI Special Agent Ron Hopper told a news conference. "I cannot comment on the outcome or the outcome of that investigation."
CNN, citing law enforcement officials, said a U.S. attorney plans to present evidence to a federal grand jury to determine whether charges will be brought against Salman. She could not be reached for comment.
In Washington, Sunday's shooting in Florida stirred fresh debate on gun purchases in the United States, as Mateen, who had expressed supported for Islamist extremism, was legally able to buy an assault rifle even though the FBI had investigated him in the past for possible ties to militant groups.
Republican presidential candidate Donald Trump said he would meet with the powerful National Rifle Association lobbying group, which has endorsed him, to discuss limited gun control measures. That marked a break with Republican Party orthodoxy, which typically opposes any restrictions on gun ownership.
The NRA responded that it believed that people listed on terrorism watch lists should face additional reviews before purchasing firearms.
Mateen's wife was with him when he cased possible targets in the past two months, including the Walt Disney World Resort in April, a shopping complex called Disney Springs and the Pulse nightclub in early June, CNN and NBC reported.
The gunman's father, Seddique Mateen, declined to comment specifically on the investigation on Wednesday, saying: "The FBI, they always do a professional job and to the maximum extent of my ability I will support them."
The younger Mateen, a New York-born U.S. citizen of Afghan heritage, was shot dead by police after a three-hour rampage through the nightclub.
Federal investigators have said Mateen, who was 29 and worked as a security guard, was likely self-radicalized and there was no evidence he received any help or instructions from outside groups such as Islamic State.
Records released by the Florida Department of Agriculture and Consumer Services show that Mateen passed a psychological evaluation in September 2007 to obtain a special state firearms license in connection with his work as a private security guard. On the license application, a psychologist certified that Mateen was "mentally and emotionally stable."
The shooting raised questions about how the United States should respond to the threat of violence from militant Islamists at home and abroad. The Federal Bureau of Investigation questioned Mateen in 2013 and 2014 for suspected ties to Islamist militants but concluded he did not pose a threat.
Sunday's attack followed a mass shooting in San Bernardino, California, in December in which a married couple inspired by Islamic State killed 14 people.
GUN CONTROL PUSH
U.S. Senator Pat Toomey, a Republican who joined Democrats in an unsuccessful push for gun control legislation after the killing of elementary school children in Connecticut in 2012, is working on a bill to keep guns out of the hands of people on terrorism watch lists, a gun control group said on Wednesday.
Democratic presidential candidate Hillary Clinton has supported gun control efforts and said on Monday she was "bewildered" that congressional Republicans had blocked a Democratic effort to restrict gun sales to people on the watch lists.
President Barack Obama and Vice President Joe Biden will visit Orlando on Thursday to meet with the families of people killed and wounded in the attack, the deadliest on U.S. soil since the hijacked plane attacks on New York and Washington on Sept. 11, 2001.
Trump has drawn vigorous criticism from Obama as well as some senior Republicans for his proposal to temporarily ban Muslims from entering the country. On Wednesday, he also called for surveillance of mosques as part of U.S. counterterrorism efforts.
Mateen made calls to 911 emergency services during his rampage, which he used to declare his allegiance to various Islamist militant groups, some of which are at odds with one another.
Orlando is one of the United States' most popular tourist destinations, with theme parks helping to draw more than 60 million visitors a year.
(Additional reporting by Barbara Liston, Bernie Woodall, Peter Eisler and Yara Bayoumy in Orlando, Fla., Ben Gruber and Zachary Fagenson in Port St. Lucie, Fla., Richard Cowan, Timothy Gardner and Susan Heavey in Washington and Alexandria Sage in Rodeo, Calif.; Writing by Scott Malone and Alistair Bell; Editing by Howard Goller and Peter Cooney)