There was a mass shooting in Orlando that turned out to be a terrorist attack. It was an attack on gay community/LGBT community, in a nightclub by the group ISIS. The terrorist was working on his own / he was a lone wolf terrorist. He said he committed the terrorist attack on behalf to ISIS, he pledges allegiance to ISIS.
He was an American-born citizen, it means that the US was confronted to a specific form of terrorism (a scarier one), which is homegrown / domestic terrorism.
It was the second time that the US was hit by domestic terrorism => San Bernardino shooting.
They decided to pay (a) tribute to the victims of Orlando by hanging rainbow flags.
9/11 (terrorist attacks) was a mark stone.
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