Washington - President Barack Obama decried the deadliest mass shooting in American history on Sunday as an "act of terror" and an "act of hate" targeting a place of "solidarity and empowerment" for gays and lesbians. He urged Americans to decide whether this is the kind of "country we want to be".Speaking hours after the shooting at a nightclub in Orlando, Obama said the FBI would investigate the shooting as terrorism, but that the alleged shooter's motivations were unclear. He said the US "must spare no effort" to determine whether the suspect, identified by authorities as Omar Mateen, had any ties to extremist groups."What is clear is he was a person filled with hatred," Obama said of the alleged shooter.Obama said this was "an especially heartbreaking day" for the lesbian, gay, bisexual and transgender community, and a sobering reminder that an attack on any American is an attack on all, regardless of their race, religion, ethnicity or sexual orientation."The shooter targeted a night club where people came together to be with friends to dance and to sing - to live," Obama said. "The place where they were attacked is more than a night club. It was a place of solidarity and empowerment, where people have come together to raise awareness, to speak their minds and to advocate for their civil rights."For Obama, the hastily arranged remarks were the latest in what's become a tragically familiar routine. Since he took office in 2009, Obama has appeared before cameras more than a dozen times following mass shootings and issued written statements after many others. The massacres have brought him to places like Newtown, Connecticut; Tucson, Arizona; and Charleston, South Carolina, to offer condolences and implore the nation to finally get serious about stemming gun violence.After a gunman in Newtown killed 20 first graders and six adults in 2012, Obama dedicated much of the start of his second term to pushing legislation to expand background checks, ban certain assault-style weapons and cap the size of ammunition clips. That measure collapsed in the Senate, and since then, the political make-up of Congress has made new gun laws appear out of reach. Still, Obama has sought to take incremental steps using his own authority to tighten rules for obtaining a gun.He signed a proclamation on Sunday ordering flags to be flown at half-staff until sunset on Thursday in honour of the victims.Meanwhile Attorney General Loretta Lynch is cutting short a visit to Beijing for cybersecurity meetings with Chinese officials and returning to the United States to monitor developments in the nightclub shooting investigation.Lynch said the Justice Department, including the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives, was supporting the investigation.IsraelPrime Minister Benjamin Netanyahu says Israel stands "shoulder to shoulder" with the United States after the shooting.Netanyahu said on Sunday that "on behalf of the people and government of Israel, I extend our deepest condolences to the American people following last night's horrific attack on the LGBT community in Orlando".He wished "heartfelt sympathies to the families of the victims" and "full and speedy recovery to the wounded."LGBT groups in Israel planned rallies and other support for the community in Orlando.Police departments across the country are meanwhile increasing patrols near locations frequented by the LGBT community.The shooting has thrust the topic of gun control back into focus as a presidential election nears.Presumptive Democratic nominee Hillary Clinton has called for expanding background checks to sales at gun shows and online purchases, and for reinstating a ban on assault weapons. Presumptive Republican nominee Donald Trump has said the existing background check system should be fixed, not expanded, and that assault-weapons bans do not work.Sunday night's Tony Awards were dedicated to those affected by the nightclub shooting. PopeThe Vatican says Pope Francis is expressing the "deepest feelings of horror and condemnation" over a massacre.Vatican spokesperson the Reverend Federico Lombardi says the pontiff denounces the "homicidal folly and senseless hatred".He added that Francis joins the families of victims and injured in the Sunday massacre in "prayer and compassion".Hundreds of people in Orlando have lined up to give blood to help the victims of the massacre.Officials at OneBlood say they have received such an overwhelming response that they are now asking donors to come back over the next several days. Florida Governor Rick Scott called the shooting "heart-wrenching" and said first responders who went into the building knowing there was an active shooter are heroic."This is clearly an act of terrorism. It's sickening. It should make every American angry."