ORLANDO, Fla. — President Barack Obama is a reluctant veteran of memorial services for mass murders, yet no single one he's presided over prepared him fully to mark the Orlando massacre.

Over two emotionally draining hours Thursday, Obama and Vice President Joe Biden met, spoke with and embraced the families of the victims, as well as some of those who survived one of the nation's deadliest mass shootings at Pulse, a gay nightclub.

He and Biden then placed 49 white roses — one for each victim — amid the other flowers, photos and balloons at a makeshift memorial.

“Their grief is beyond description,” Obama told reporters after meeting with the families. Then, appearing to break away from his prepared text, he renewed a call for the country to change the debate over guns.

Fathers and mothers, sisters and brothers had shared their loved ones' stories, Obama said. But they also asked why such tragedies keep happening. They pleaded with him to do more.

“They don't care about the politics. Neither do I,” Obama said.

“This debate needs to change. It's outgrown the old political stalemates,” he said.

Obama also challenged his potential Republican successor without naming him, saying the idea that fewer lives would have been lost had more patrons at the Pulse nightclub been armed “defies common sense.”

The Orlando attack stands distinct in the president's experience for its scope and scale, but also for the complex web of issues it brought to the forefront — fear of terrorism and radicalism, worries about political fallout and the vulnerability of targeted communities.

Unlike some of the president's previous trips for memorial services after mass shootings, this one was decidedly low-key: no address to a large crowd, but simply what White House officials had said would be “a few personal reflections” to the media after spending time with mourners.

The White House worked with Orlando Mayor Buddy Dyer to coordinate the visit, spokesman Eric Schultz told reporters traveling with the president, and did not want to overburden local law enforcement officials strained by the attacks.

While the shooting had quickly become fodder for the presidential campaign, Obama's visit had a bipartisan note. Sen. Marco Rubio, R-Fla., joined Obama aboard Air Force One to travel to Orlando. And among those greeting Obama upon arrival was Republican Gov. Rick Scott.

For Obama, the gathering reprised a memorial like the one in Newtown, Conn., in 2012. Obama met with almost every immediate family member who lost a child at Sandy Hook Elementary School in that massacre, and the experience fueled his ultimately doomed effort to pass gun control legislation afterward.

Although Obama sees Orlando as a singular moment, he approached it with the heavy baggage of the mass shootings that have come before it during his presidency.

The fact that he was speaking to and about lesbian, gay, bisexual and transgender people and immigrants, communities who may feel their equality and liberty are under fire, added to the urgency of his visit.

“These families could be our families. In fact, they are our family, they're part of the American family,” he said.

Pulse was a “sanctuary,” Obama noted, one that was “violated in the worst way imaginable.”

It was an act of terror, Obama said, but also an act of hate.

The 29-year-old gunman, a New York City native named Omar Mateen, had spoken in the past of his hatred for gay people, racial minorities and Jews. In the midst of the massacre at the nightclub he called a 911 operator and announced his loyalty to Islamic State, though investigators are still probing whether he had contact with the extremist group.

Whatever his motivations, Obama said, “hatred toward people because of sexual orientation, regardless of where it comes from, is a betrayal of what's best in us.”

“If there was ever a moment for all of us to reflect and reaffirm our most basic beliefs that everybody counts and everybody has dignity, now is the time.”

Still, Obama said he found solace in the response of the Orlando community and in the lives cut too short.

“Out of this darkest of moments, that gives us hope — seeing people reflect, seeing people's best instincts come out, maybe in some cases, minds and hearts change,” he said.

Christi Parsons reported from Orlando and Michael A. Memoli from Washington.

cparsons@tribune.com