Roundup: Americans condemn Orlando mass shooting while politicians argue over precautions

Volunteers queued for hours in heavy rain to donate blood at mobile stations in Orlando, Florida, where the deadliest U.S. mass shooting to date took place on Sunday, while politicians argued from the very wording of the incident to ways to prevent the recurrence of such tragedy.

At least 50 people were killed and 53 others wounded, including a police officer in the attack early Sunday.

The tragedy happened amid a series of events nationwide in celebration of LGBT (lesbian, gay, bisexual and transgender) Pride Month. In several other cities hosting events on Sunday, including block parties in Boston and a festival in Washington, police strengthened security. In Los Angeles, about 100,000 people marched in a planned Gay Pride parade in defiance of the bloodshed.

U.S. President Barack Obama denounced the Orlando shooting as an "act of terror and an act of hate," in a national address in Washington on Sunday afternoon. He said the country must spare no effort to determine whether the killer had any ties to extremist groups.

In the presidential race, the two hot presidential candidates, Donald Trump and Hillary Clinton, also aired their views on the killings in hopes of attracting more voters.

Trump called for Obama's resignation for refusing to use the words "radical Islam" in his address, adding that his rival Clinton should quit from the presidential race for the same reason.

Clinton said in a statement that "To the LGBT community: please know that you have millions of allies across our country. I am one of them," adding a call to keep assault weapons out of the hands of "terrorists or other violent criminals."

On the other side, Trump renewed talk of his plan to ban Muslims from the United States for an indeterminate time.

Mike Rawlings, the mayor of Dallas, said that the incident "is a tragic illustration of the legitimate safety fears that those in our LGBT community live with every day."

Speaking at the Houston LGBT Caucus event on Sunday, Houston Mayor Sylvester Turner said that it is the time "when all of us stand together and say to the world that we will not tolerate these types of violence anywhere in this country."

"Enough of people talking about other groups as if they have no value and they're not worth anything. And enough of people being silent and letting folks do it and say what they want to say ... Now we must draw the line," Turner said.

Former Houston Mayor Annise Parker, the first openly gay mayor of a major U.S. city, also said at the event that it is not the first time "our community or many other communities have had to stand and acknowledge a terrible, terrible incident."

He said that fear should never drive people's decisions or make them strike out against any other community.

LGBT organization Pride Houston said in a statement: "Our thoughts and hearts are with the victims, their families and friends affected by this senseless tragedy."

Frankie Quijano, CEO of Pride Houston, said: "Today is a tragic loss for the LGBT community, and we keep the victims, as well as those affected, in our hearts as we move forward together as a community."

He said that there will be an increased presence of Houston police and additional security officers throughout Houston LGBT Pride Celebration, which is scheduled for June 25.

The Council on American-Islamic Relations, a leading Muslim civil rights advocate group in the United States, said in a statement: "The Muslim community joins our fellow Americans in repudiating anyone or any group that would claim to justify or excuse such an appalling act of violence."

The suspected Orlando night club shooter Omar Mateen was a security guard in West Palm Beach with G4S. In a statement sent to the Palm Beach Post, the security company said: "We are cooperating fully with all law enforcement authorities, including the FBI, as they conduct their investigation." Endi