The rampage also reverberated on the presidential campaign trail, as the leading presidential candidates offered dueling speeches Monday that pivoted off the attack.

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Donald Trump, the presumptive GOP nominee, called for a ban on immigrants from any area of the world with a history of terrorist attacks against the United States, going beyond his previous calls to bar Muslims from traveling to the country. In her own remarks, Hillary Clinton, the expected Democratic nominee, said stronger gun control laws were needed to prevent suspected terrorists from having access to weapons.

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While law enforcement officials were still working to determine what motivated the gunman — 29-year-old Omar Mateen — the FBI said Monday that he had been placed on a terrorism watch list during a 10-month period in 2013 and 2014 after he was investigated for inflammatory comments he made to co-workers.

During a three-hour hostage standoff with police after the shooting spree Sunday, Mateen referenced the Islamic State, and the militant group — also known as ISIS or ISIL — claimed Monday that Mateen was a “soldier” for its self-proclaimed caliphage. However, officials say that so far, no signs have emerged that he was guided by groups outside the country.

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“We see no clear evidence that he was directed externally,” Obama said during remarks in the Oval Office. “It does appear that at the last minute, he announced allegiance to ISIL. But there is no evidence so far that he was in fact directed by ISIL, and at this stage there’s no direct evidence that he was part of a larger plot.”

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Obama said the shooting appeared so far to be a case of “homegrown extremism.”

The comments by Obama and other law enforcement officials Monday offered the sharpest look yet at what authorities believe may have motivated the gunman who attacked Pulse, a popular gay club in Orlando.

“We’re working hard to understand the killer, and his motives, and his sources of inspiration,” FBI Director James B. Comey said Monday. “We’re highly confident that this killer was radicalized, and at least in some part through the Internet.”

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Even as this information emerged, police were still revealing details about the shooting and the hostage situation that followed, while relatives of victims were still awaiting word about whether their loved ones were among the wounded or dead.

Comey said that during the three-hour standoff the gunman had with Orlando police officers, there were three different 911-related calls. The gunman called 911 about half an hour after opening fire and then hung up the phone, Comey said. Mateen then called a second time and spoke briefly to a dispatcher before hanging up again, and then the dispatcher called him back and they spoke briefly.

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“During the calls, he said he was doing this for the leader of ISIL, who he named and pledged loyalty to,” Comey said.

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However, Comey said there were no signs that Mateen was tied to any kind of network, and he added that it remained unclear exactly what extremist group this attacker supported.

In addition to referencing the Islamic State, Mateen also mentioned the Boston Marathon bombers as well as a Florida man who had joined an al-Qaeda affiliate and carried out a suicide attack in Syria, leaving his specific sympathies unknown, Comey said.

Law enforcement officials in Florida, meanwhile, offered a new accounting of the shootout. Orlando Police Chief John Mina said that police first encountered Mateen shortly after the initial gunfire at about 2 a.m., when an off-duty officer working at the club — Adam Gruler, a 15-year veteran of the force — exchanged shots with Mateen.

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The scene in Orlando after a gunman opened fire at a nightclub share Share View Photos View Photos Next Image An injured person is escorted out of the Pulse nightclub after a shooting rampage, Sunday morning June 12, 2016, in Orlando, Fla. A gunman wielding an assault-type rifle and a handgun opened fire inside a crowded gay nightclub early Sunday, killing at least 50 people before dying in a gunfight with SWAT officers, police said. It was the deadliest mass shooting in American history. (AP Photo/Steven Fernandez)

Additional officers called to the scene soon joined in another gun battle, at which point Mateen retreated further into the building and, eventually, into a bathroom. The police then held back because there were no more gunshots, Mina said, and they tried to negotiate with Mateen to avoid any more bloodshed.

Mateen was in a bathroom with four or five people, while another 15 or 20 were in another bathroom, Mina said. During these negotiations, Mateen was “cool and calm” and did not make many demands, Mina said.

After about three hours, police said they decided to storm Pulse after the shooter referenced bomb belts or explosives. Mina said the police used explosives and then an armored Bearcat to break a hole in the club’s wall. Hostages poured out, and Mateen — armed with a pair of guns — came out as well.

During the gun battle, Mateen was killed and one Orlando police officer — Michael Napolitano, a 14-year veteran of the force — was injured when a bullet struck his Kevlar helmet. In a statement Monday, police identified Napolitano and the other officers who fired shots at the nightclub. Following state protocol, all 11 of these officers have been relieved of duty while the state investigates their shootings.

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However, much still remains unclear, including whether any hostages might have been injured or killed by crossfire.

In a news conference Monday, Mina said storming the building “was the right decision to make” because police thought other lives might be in danger.

Authorities say they are continuing to explore whether other people may be connected to the case. The investigation into Mateen has expanded to look at other people, and it stretches from Florida to Kabul.

Investigators also said Monday that they had found a third gun in Mateen’s car and were working to trace its origins after learning that the two weapons he had during the shooting — a handgun and an assault-rifle-type weapon — were purchased legally.

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There is now “an investigation of other persons,” A. Lee Bentley III, the U.S. attorney for much of Central Florida, said at a news conference Monday. Bentley said prosecutors have “no reason to believe that anyone connected to this crime is placing the public in imminent danger,” but he offered no other details.

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“We’ve been collecting a great amount of electronic and physical evidence,” Bentley said Monday. The FBI also said Monday that investigators have processed more than 100 leads so far.

Authorities said Monday afternoon that they had identified relatives or next-of-kin for nearly all of the victims, making notifications for 48 of the 49 people killed. (On Sunday, police had included Mateen when saying 50 people were killed.) For many, the hours stretching from Sunday into Monday were filled with dread as they awaited word about whether their loved ones were among the wounded or dead.

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All the bodies were removed from the club by 11 p.m. Sunday, authorities said.

Orlando Regional Medical Center, where many shooting victims were taken, said Monday that the hospital was still treating 29 people, including five who were “in grave condition.” A number of victims were in critical condition or in shock, the hospital said. Hospital officials also said local blood banks had more than 600 units on hand due to the surge in people who donated blood after the shootings.

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As the investigation into Mateen moved into its second day, many questions remained unanswered — including what, specifically, might have motivated him. Bentley said investigators were serving search warrants, and the FBI asked anyone with information about the 29-year-old’s life to call 1-800-CALLFBI.

In Orlando and beyond, the investigation was still trying to determine the steps that led up to the attack Sunday.

Comey said the FBI was working to determine the role anti-gay bigotry may have played in Mateen’s choice of a target. The Islamic State has carried out a relentless campaign against gay people, releasing videos showing its members gruesomely executing people they said were homosexual.

Mateen had been on the FBI’s radar twice in recent years. In 2013, agents opened an investigation that lasted 10 months after Mateen made comments to co-workers about terrorist groups and expressed a desire to martyr himself.

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Investigators interviewed him twice, but Mateen said he made the remarks in anger because he felt co-workers were teasing him for being Muslim, and the preliminary inquiry was closed in 2014, Comey said.

Two months later, Mateen again came to the attention of federal agents looking into the Florida man who blew himself up in Syria, Comey said. Mateen and this man attended the same mosque, according to Comey. Again, the FBI interviewed Mateen, looked into his possible ties to the suicide bomber, determined that there were no strong ties and moved on.

Even given Mateen’s mentions of the Islamic State, the level of possible connections between the gunman and the militant group were unclear.

The Islamic State’s al-Bayan Radio described him Monday as “one of the soldiers” of its self-described caliphate, but it offered no further details on possible contact before the attack, said the SITE Intelligence Group, which monitors statements by extremist factions.

If it does appear that the Orlando gunman was radicalized from material available online, it would follow a pattern seen in earlier shooting rampages in San Bernardino, Calif., and Chattanooga, Tenn., last year.

A U.S. official, speaking to reporters on condition of anonymity to discuss intelligence assessments, said that attacks inspired by the Islamic State, even when conducted without support from the group’s core operation, helped illustrate to followers that they remained a significant military force despite loss of territory in Iraq and Syria over the last year.

“In a sense, inspired attacks and attacks conducted in their name globally” allows them to perpetuate a key perception: continued expansion, the official said. Such attacks show would-be supporters that “they’re very much still alive and potent.”

Secretary of Defense Ashton B. Carter, speaking en route to Brussels, told reporters that the shooting should “further steel everyone’s resolve to defeat ISIL and its parent tumors in Iraq and Syria.”

As terrorism again surged to the forefront of the country’s political debate, Trump and Clinton shifted plans for events Monday to focus their remarks on national security.

Clinton, speaking in Cleveland, warned that the threat posed by the Islamic State is “metastasizing” and vowed to make “targeting lone wolves a top priority” if elected.

She also said that someone who has been watched by the FBI “shouldn’t be able to just go buy a gun with no questions asked.” Clinton, echoing remarks Obama has made, also said the shooting was a reminder of the need for stronger gun control laws.

“It’s essential that we stop terrorists from getting the tools they need to carry out attacks,” she said. “I believe weapons of war have no place on our streets.”

Before his speech in New Hampshire, Trump made television appearances to reject calls for more gun control and repeatedly accuse Obama of being somehow sympathetic with radicalized Muslims.

“We’re led by a man that either is not tough, not smart, or he’s got something else in mind,” Trump said.

Orlando now joins the mournful list of terrorism-linked bloodshed — Brussels in March, Paris and San Bernardino last year, the Boston Marathon in 2013, London in 2005 and other sites — and is certain to strike deep into American debates over gun rights and how far authorities can go to track potential terrorism threats. And the shooting struck a popular gay club on its Latin night.

From around the world, condolences and pledges of support poured in. Vigils and memorials were held from New Zealand to Europe. The Eiffel Tower will be lit in rainbow colors Monday evening.

In Afghanistan, the country’s chief executive, Abdullah Abdullah, said the Orlando attack “tells us that terrorism knows no religion, boundary and geography. Terrorism must be eliminated.”

Officials in Afghanistan — Mateen was born in the United States, while his parents were born there — also opened investigations into any possible connections between the gunman and militant groups. Yet Mateen’s father insisted his son had no Islamist terrorism ties and showed no warning signs the day before the shooting.

Mateen had legally purchased the two guns — which the Bureau of Alcohol, Tobacco, Firearms and Explosives said were an ­AR-15-type weapon and a 9mm semiautomatic pistol — within “the last few days,” according to Trevor Velinor of the ATF.

A U.S. official, speaking on the condition of anonymity to discuss the investigation, said the FBI had found nothing in Mateen’s past that would have legally blocked him from purchasing a gun. The bureau’s previous inquiries, the official said, would have been insufficient to achieve that.

Mateen purchased two guns from the St. Lucie Shooting Center, shop owner Ed Henson said at a news conference Monday.

“An evil person came in here and legally purchased two firearms from us,” Henson said, adding that Mateen had multiple security licenses and passed a full background check before he was allowed to buy the guns.

Henson said if Mateen hadn’t bought the guns at his shop, he would have been able to buy them somewhere else.

“We happened to be the gun store he picked. It’s horrible,” said Henson, who spent two decades with the New York Police Department before retiring in 2002. “I’m sorry he picked my place. I wish he’d picked nowhere.”

Mateen’s ex-wife, Sitora Yusifiy, said he beat her repeatedly during their brief marriage, and she called him unstable.

Mateen’s father, however, called his son “very dignified.” In a video posted to Facebook shortly after midnight, Seddique Mateen, who lives in Florida, called the shooting “tragic” but said his son was “a good son and an educated son.”

He said his son shouldn’t have carried out the massacre because “God himself will punish those involved in homosexuality.”

“I don’t know what caused him to shoot last night,” said the father, who has hosted a U.S. -based television show on Afghan affairs and describes himself as an important figure in his homeland.

“No radicalism, no,” the father told The Washington Post late Sunday from his home in Port St. Lucie, Fla. “He doesn’t have a beard even. . . . I don’t think religion or Islam had anything to do with this.”

Berman reported from Washington. Emma Brown, Brian Murphy, Jenna Johnson, Missy Ryan, Adam Goldman and Jerry Markon in Washington; Katie Zezima, Hayley Tsukayama and Amanda Elder in Orlando; Abby Phillip in Cleveland; and Thomas Gibbons-Neff in Brussels contributed to this report. Also contributing: Greg Miller, Joby Warrick, Tim Craig, Sarah Larimer and Julie Tate.

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