Mrs Long was speaking in the Assembly on Monday.
“Anyone who has read of the horror of the last moments of those in the Pulse nightclub Orlando could not be anything but moved,” she said.
“My thoughts are with the families and friends of those killed and injured. I also stand in solidarity with the wider LGBT community in Orlando, in the US and here at home. When a safe space for LGBT people is violated in this way, the ripples of fear are not just local, but global.
“Our response must be to stand against homophobia, terrorism and violence and for the values of an open, liberal and tolerant democracy which also were under attack. Action to build that kind of society at home and abroad will be our best tribute to the victims.”