President Trump said Friday that he has offered U.S. aid to New Zealand after Thursday night's shooting massacre at two mosques that killed 49 worshippers.The president wrote in a pair of tweets that he spoke to New Zealand Prime Minister Jacinda Ardern "regarding the horrific events that have taken place over the past 24 hours."The prime minister called the attack one of New Zealand's "darkest days" at a press conference on Friday."I informed the Prime Minister that we stand in solidarity with New Zealand – and that any assistance the U.S.A. can give, we stand by ready to help," Trump said. "We love you New Zealand!"A gunman opened fire on two mosques in Christchurch, New Zealand around lunchtime local time, killing 49 and wounding at least 20, including young children. He streamed video of the attack live online.The attacker, a 28-year-old Australian white man, posted a white supremacist manifesto of sorts on the message board 8chan, one of the darkest corners of the internet, warning he was planning “an attack against the invaders,” referring to Muslims.Three people including the gunman were arrested, and the gunman has been charged with murder. He will appear in court Saturday morning.Despite the attacker's statements saying he was motivated by a white supremacist ideology, Trump maintained that he does not believe the credo is on the rise in the U.S.Asked at the White House whether he sees white nationalism as a "rising threat around the world," the president responded “I don’t, really.”"It’s a small group of people that have very, very serious problems," Trump said, adding that he "did not see" the gunman's manifesto, which appeared to make reference to Trump as a "symbol of renewed white identity and common purpose.""I guess, if you look at what happened in New Zealand, perhaps that’s a case," Trump continued. "I don’t know enough about it yet, they’re just learning about the person and the people involved. But it’s certainly a terrible thing.”