(AP) -- The Latest on the Florida nightclub shooting. (all times local):

7:40 a.m.

Homeland Security Secretary Jeh (jay) Johnson says Republican Donald Trump's proposal for a ban on immigration from countries with terrorist histories is impractical.

While declining to name Trump, Johnson condemned "overly simplistic suggestions" for dealing with the violence.

Appearing on ABC's "Good Morning America," Johnson defended President Barack Obama against Trump's charge that Obama has been too passive on the issue.

Johnson said that "I know from working with him for seven years that the president's No. 1 priority is the protection of Americans."

He added that authorities throughout the government continually reassess whether their strategy to combat this violence needs to be changed.

Johnson told ABC that protecting U.S. from attack is increasingly complicated in an era of "self-radicalization." He said "there's no indication" the Orlando attack was "terrorist-directed."

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7:25 a.m.

Officials with an agency that collects blood donations across much of Florida continue to urge people to give blood in the wake of the Orlando nightclub massacre.

Potential donors are asked to make appointments at their local blood banks.

OneBlood officials posted videos on Facebook showing snacks and beverages donated for people waiting in long lines to give blood. Spokeswoman Stephanie Zaurin says donors are coming "in record numbers."

U.S. Food and Drug Administration spokeswoman Tara Goodin said in an email to The Associated Press that the Interorganizational Disaster Task Force met Sunday and ensured that all immediate needs for blood were met.

Goodwin said the agency appreciated the widespread desire to donate blood after the shooting at Pulse. She said scheduling appointments to donate blood "will help replenish the blood supply in an organized manner, without overwhelming the system."

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7:10 a.m.

As they got back to work after the Sunday nightclub massacre, TV's late-night hosts faced the challenge of how to acknowledge it.

As in past tragedies, the jokesters shifted gears. Several opened their shows with apologies for departing from their customary monologues, instead voicing shock and sorrow.

"The Daily Show" host Trevor Noah pointed out that President Barack Obama has hosted 12 state dinners but 16 mass-shooting addresses. Noah raised the possibility that, without reasonable gun control, Obama should begin preparing Speech No. 17.

"The Late Show" host Stephen Colbert bemoaned "a national script" that seems to guide a nonproductive response to shootings. He declared that love could help Americans change that script.

Conan O'Brien, while noting that he had made a career-long policy of keeping political opinions to himself, expressed bewilderment that anyone is allowed to buy a semi-automatic assault rifle. He said, "These are weapons of war and they have no place in civilian life."

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6:50 a.m.

The office of the U.N. human rights chief is decrying "insufficient gun control" in the United States and urging its leaders "to live up to its obligations to protect its citizens."

In the wake of a gunman's deadly attack on a Florida nightclub, Zeid Ra'ad al-Hussein criticized "irresponsible pro-gun propaganda" in the U.S. claiming that firearms make society safer, "when all evidence points to the contrary." He questioned the ease with which people in the U.S. can obtain firearms and assault weapons like one used in Sunday's attack.

Citing a U.N. report on firearms in April, Zeid pointed to examples of how control of firearms in many countries led to a "dramatic reduction in violent crime."

Office spokesman Rupert Colville told reporters Tuesday in Geneva: "The problem is the guns."

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5:20 a.m.

Jim Van Horn said he was a frequent patron at Orlando's Pulse night club. He said another "regular" at the Florida gay bar was Omar Mateen, the man whose shooting rampage left 49 dead and dozens more wounded early Sunday in the worst mass shooting in modern U.S. history.

Speaking to The Associated Press late Monday, 71-year-old Van Horn says he saw Mateen trying to pick up men at the club.

Van Horn said he met Mateen once. He said the younger man was telling him about his ex-wife.

Van Horn says some friends then called him away and told him they didn't want him talking to Mateen because "they thought he was a strange person."

Despite Mateen's pledge of support to the Islamic State, other possible explanations emerged, including questions of whether he was conflicted about his sexuality.

His ex-wife said he suffered from mental illness. And his Afghan-immigrant father suggested he may have acted out of anti-gay hatred.

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3:15 a.m.

Thousands in Orlando are mourning 49 people killed inside a gay nightclub as federal investigators examine possible motives for the gunman who committed the worst mass shooting in modern U.S. history.

The White House and the FBI said 29-year-old Omar Mateen, an American born Muslim, appears to be a "homegrown extremist" who had touted support not just for the Islamic State, but other radical groups that are its enemies.

Meanwhile, Mateen's ex-wife says he suffered from mental illness. And his Afghan-immigrant father says his son got angry recently about seeing two men kiss.

Meanwhile, thousands gathered Monday night in downtown Orlando for a vigil to support victims and survivors of the Pulse nightclub shooting on the lawn of Orlando's main performing arts venue.