Republican US presidential candidate Donald Trump speaks as his daughter Ivanka, left, looks on at a campaign event at the Trump National Golf Club Westchester in Briarcliff Manor, New York, June 7, 2016. Reuters/Carlo Allegri Following a horrific shooting at a LGBT club in Orlando, Florida, that left 50 people dead on Sunday morning, Donald Trump boasted that he was right to warn about the danger of violent extremism.

In a tweet on Sunday afternoon, the presumptive Republican presidential nominee said he was thankful for supporters who congratulated him for "being right" about the dangers of terrorist acts committed by extremists.

"Appreciate the congrats for being right on radical Islamic terrorism, I don't want congrats, I want toughness & vigilance. We must be smart!" Trump wrote.

Law enforcement confirmed on Sunday that the incident is being treated as an act of terrorism, but some officials told Reuters that as of early Sunday afternoon, they had not uncovered direct contacts between the gunman and any extremist group

In a press conference on Sunday, Florida Sen. Bill Nelson said that the suspected shooter had "some connection to ISIS," though it was not clear if there were official ties.

For her part, presumptive Democratic presidential nominee Hillary Clinton was more reserved in her response on Twitter to the shooting.

Trump has been willing to go further than many public officials in his proposals to attempt to counter perceived threats from extremists with ties to ISIS.

Last year, Trump ignited a firestorm of controversy when he announced a plan to bar all Muslims from entering the US until the country could "figure out what's going on."