ORLANDO — President Obama met Thursday afternoon with relatives of people killed in the recent shooting rampage here as well as with survivors of the attack, again making a grim pilgrimage to mourn a mass killing and try to console those left behind. He also again called on lawmakers to pass stronger gun control laws, urging them to help “end the plague of violence that these weapons inflict on so many lives.”

While laying flowers at a memorial in downtown, about a mile and a half from the club where the shooting occurred four days earlier, Obama said the city was “shaken by an evil, hateful act.” Obama said that when he and Vice President Biden met with family members of the people slain on Sunday, their grief was indescribable.

“The Vice President and I told them, on behalf of the American people, that our hearts are broken, too, but we stand with you and that we are here for you, and that we are remembering those who you loved so deeply,” Obama said of the meeting.

Even as this visit — the latest in what has become a long line of trips he has made to regions rocked by catastrophic gun violence — was underway, discussions continued on Capitol Hill about holding votes on gun-control measures following a nearly 15-hour filibuster on the Senate floor. Obama said he hoped senators who had previously opposed some measures “have a change of heart,” saying that the relatives he met with on Thursday asked why such killing sprees keep happening.

The rampage early Sunday at Pulse, a gay nightclub, left 49 people dead and dozens more injured. Hours before Obama arrived, officials in Orlando said that nearly two dozen people injured in the shooting were still hospitalized, six of them in critical condition.

Three others were in “guarded” condition, while the rest were stable, according to Orlando Regional Medical Center, where many of the victims were taken. The hospital said its surgeons had performed 50 operations in the four days since the shooting, with more scheduled for Thursday.

“This healing process is not going to happen overnight,” Schultz told reporters on Air Force One. “It’s not going to be a quick one. That’s all the more reason why the president wanted to be there in person.”

Obama was joined on the flight by two Florida lawmakers — Sen. Marco Rubio (R) and Rep. Corrine Brown (D) — while another, Sen. Bill Nelson (D), flew down with Biden, officials said. When Obama arrived in Orlando, he shook hands with Gov. Rick Scott (R) and greeted Mayor Buddy Dyer (D), who was wearing an “Orlando United” T-shirt.

While in Orlando, Obama and Biden met with different groups, thanking law enforcement officials for how they acted in responding to the shooting and gathering with people who were working at Pulse when the gunfire began. The motorcade traveled to the Amway Center in downtown Orlando so that Obama and Biden could be with survivors and relatives of those who died, a meeting that has become all too familiar during his presidency.

“Today, once again, as has been true too many times before, I held and hugged grieving family members and parents, and they asked, why does this keep happening?” Obama said Thursday. “And they pleaded that we do more to stop the carnage.”

After that gathering, Obama and Biden traveled to the memorial at the Dr. Phillips Center for the Performing Arts, where a wide swath of land was covered with balloons, flowers and other tributes.

An American flag embroidered with the names of those killed sat among the photos of the dead, pinwheels and other mementos that packed the ground, the balloons bobbing in the afternoon breeze. One arrangement was from Dyer and city hall staff. Many signs around the memorial read “Orlando strong,” while one, apparently written by a child, said, “Never lose hope, love and compassion.”

Obama and Biden laid flowers, one for each person killed in the rampage, and knelt next to the public remembrances of those who died.

In remarks at the memorial, Obama called the shooting a lone-wolf attack. But he also invoked the mass killings in a movie theater in Aurora, Colo., and Newtown, Conn., and again said these rampages showed why stronger gun control laws were needed.

“Those who were killed and injured here were gunned down by a single killer with a powerful assault weapon,” Obama said. “The motives of this killer may have been different than the mass killers in Aurora, or Newtown. But the instruments of death were so similar. Now another 49 innocent people are dead. Another 53 are injured. Some are still fighting for their lives.”

He continued: “We can’t anticipate or catch every single deranged person … but we can do something about the amount of damage that they do.”

After president Obama and Biden left the memorial, onlookers sprinted across the plaza in front of the Dr. Phillips Center to see the flowers they left: two very large bouquets of white roses.

“Come touch the flowers Barack touched,” Nicole Batey said to her 8-year-old daughter Adrianna.

“Can I?” The girl asked.

Her mother told her yes and she did. She wanted her daughter to touch them and be part of history.

“It’s such a tragic time but it shows his solidarity when we needed him,” Batey said, winded from sprinting in 91-degree heat. “It just means so much. It’s just been a sad few days, a sad week for us in Orlando … It shows that he cares.”

As Obama’s motorcade rolled by, a throng of people cheered. Justin Kane, 23, came down from his nearby office.

“I wanted to come show my respects for why he’s here,” Kane said. “Parties aside we appreciate the most powerful man on earth for coming down and paying his respects.”

Lisa Crews, 52, had come to pay her respects at the memorial earlier on Thursday.

“I think it’s for looks,” she said of Obama’s visit.

While Mike Donahue, 27, paid tribute at the memorial to two friends killed in the shooting, he said he was happy Obama came to Orlando. “I hope it helps” the city, families and victims, Donahue said.

“I think it’s a good thing that leaders come after tragedies,” he said of Obama and Biden. “They show they’re supportive. And they’re from a party that did a really good thing on the Senate floor last night.”

A bouncer from Pulse nightclub in Orlando is one of the first to be laid to rest in the continental U.S. (Reuters)

While those who lost loved ones in the attacks have begun attending the first of what will be a long succession of memorials and funerals, investigators sought to piece together what motivated the gunman and how he spent the months leading up to the attack.

The attacker — 29-year-old Omar Mateen — posted that day on Facebook about the Islamic State, pledging allegiance to the group’s leader and claiming that the shooting was “vengeance” for airstrikes, according to Sen. Ron Johnson (R-Wis.), chairman of the Senate Homeland Security Committee.

In a letter sent Wednesday to Facebook, Johnson wrote that Mateen had previously used the social network to search for information about the Islamic State’s leader and the San Bernardino, Calif., terrorist attack. After the shooting, though, he searched for news about “Pulse Orlando” and “Shooting,” Johnson wrote.

The postings on Facebook were made within minutes of the initial shooting at about 2 a.m., according to an individual familiar with the investigation. And the searches on Facebook for news about the attack were made during the three-hour window that followed, when Mateen held hostages inside before police stormed the building at 5 a.m.

Facebook is cooperating with the FBI, according to the person familiar with the probe, who asked not to be identified discussing an ongoing investigation.

Authorities are sorting through a hornet’s nest of possible motivations and explanations, sifting through the gunman’s pledges of loyalty to the Islamic State, his prior claims about other militant groups, the possibility that anti-gay sentiment motivated his attack and the added fact that witnesses say they had previously seen him on gay dating apps and at the club.

New details continue to emerge about what he said and did after the shooting. While Johnson’s letter to Facebook did not explicitly say when the shooter posted about the Islamic State, he said these postings occurred on Sunday. The shooting took place at about 2 a.m. Sunday. After a three-hour hostage standoff with police, the gunman was killed in a shootout with officers.

In a grim echo of the attacks in San Bernardino, the gunman used Facebook the day of the shooting to pledge loyalty to Abu Bakr al-Baghdadi, the emir of the self-proclaimed Islamic State.

“America and Russia stop bombing the Islamic state..I pledge my alliance to abu bakr al Baghdadi..may Allah accept me,” Mateen posted, according to Johnson’s letter, which requested Facebook’s assistance in the investigation.

He then posted “The real muslims will never accept the filthy ways of the west” and “You kill innocent women and children by doing us airstrikes..now taste the Islamic state vengeance.” In a final post, Mateen apparently wrote, “In the next few days you will see attacks from the Islamic state in the usa.”

The social media postings corroborate accounts that Mateen was motivated in part by a perceived connection to the Islamic State. Mateen also pledged allegiance to the leader of the Islamic State during 911 calls, although he also apparently mentioned the Boston Marathon bombers.

FBI Director James B. Comey said earlier this week that there were no signs that Mateen was directly tied to any kind of network, and he added that it was still not clear exactly which extremist group he supported.

Mateen’s references to terrorist groups have at times been muddled. Officials say he made comments in recent years to co-workers claiming he had family connections to ­al-Qaeda and was a member of Hezbollah, two opposing terrorist groups that have clashed repeatedly in Syria.

Mateen also apparently used Facebook in May to look for information on the terrorists behind the 2015 San Bernardino attack. On June 4, 2016, a little more than a week before the Pulse shooting, he searched “Baghdadi Speech,” according to Johnson’s letter.

Authorities seeking answers about the gunman say they  have expanded the investigation to include interviews with his relatives, friends and anyone else who may have had contact with him in the months before the attack.

As investigators continue probing Mateen’s life, they are also scouring digital forensics and are trying to reconstruct his actions dating back months. Meanwhile, evidence technicians were methodically tracing the path of the barrage of bullets that flew inside Pulse as they attempted to diagram precisely what happened.

Mateen appeared to be a skilled shooter, according to documents released Wednesday, repeatedly scoring high marks on tests needed to obtain firearms licenses. According to records dating to last year, Mateen had smoked marijuana, used steroids and had been expelled from high school in the ninth grade for fighting.

In these records, Mateen said he had been convicted of a crime, placed on probation and had a criminal conviction sealed or expunged. He did not specify the offense. He said he spoke excellent Farsi and good Arabic.

Asked why he had never served in the U.S. military, Mateen said that he “wanted to stay close to family.”

Reached by telephone Wednesday evening, Mateen’s mother, Shahla Mateen, said she knew nothing of her son’s plans.

“No. Nothing. Nothing,” she said.

Mourners in Orlando tell leaders and lawmakers in the nation's capital what the country needs to stop the next mass shooting. (McKenna Ewen/The Washington Post)

While the FBI said it views the shooting as a hate crime as well as an act of terrorism, officials said there were “no impending charges” in the case and declined to discuss whether any were forthcoming.

The FBI confirmed that it had interviewed Noor Z. Salman, Mateen’s wife. She urged her husband not to do anything the night of the attack, said one U.S. law enforcement official. But the bureau also tried to play down this element of the investigation, saying it was part of the larger work of piecing together the gunman’s movements and motivations.

“With respect to the wife,” Ronald Hopper, an FBI assistant special agent in charge, said Wednesday, “that is only one of many interviews we’re doing.”

Salman has not publicly commented on the attack, and she has not been seen since Monday night, when the Miami-based television station WSVN recorded video of the 30-year-old being escorted from her home in Fort Pierce, Fla. Her face was shrouded by the hood of her sweatshirt, and her left hand had what appeared to be a silver wedding band.

She had accompanied Mateen at one point to buy ammunition and went with him on at least one trip to Pulse described as “reconnaissance” not long before the shooting, according to officials familiar with the investigation who spoke on the condition of anonymity to discuss the ongoing probe. Whether she knew the purpose of that trip remains unclear.

Investigators are still working to corroborate what Salman told them during interviews, according to authorities, and will also try to determine if she suffered any abuse at the gunman’s hands. His first wife — Sitora Yusifiy, to whom he was briefly married in 2009 — said he beat her repeatedly while they were married. How authorities ultimately view Salman’s role and actions could change if she was a victim of abuse or feared for her life, officials say.

“We’re looking at everything,” Hopper said.

He also said authorities had found no evidence yet that Mateen intended to target any other locations, and officials said they had no information about any possible surveillance at Disney or any knowledge of Mateen patronizing clubs besides Pulse.

Mateen’s phone has been recovered, and forensic experts were about to access the data, an official said.

Nakashima and Berman reported from Washington. Juliet Eilperin, David Nakamura, Adam Goldman, Jennifer Jenkins, Brian Murphy and Julie Tate in Washington and Matt Zapotosky and Kevin Sullivan in Orlando contributed to this report.