Not to be picky and ruin your joy of shoving pencils in your dick hole every time Trump opens his yuge yapper, but it doesn't appear he said anything about a terror attack as your thread title suggests. This is what I found that he said...
“You look at what’s happening in Germany, you look at what’s happening last night in Sweden, Sweden. Who would believe this? Sweden. They took in large numbers. They’re having problems like they never thought possible. You look at what’s happening in Brussels. You look at what’s happening all over the world. Take a look at Nice. Take a look at Paris."
(I'll preface this by saying you're likely right, and the next part is simply devil's advocate.)
Although he likely was just mindlessly gum flapping, he could have been referring to several things reported out of Sweden on the 17th such as:
http://madworldnews.com/muslim-refugee-impregnates-child/
http://pamelageller.com/2017/02/refugee-savage.html/
I did this quickly and only glanced through the stories. They could be fake news like your thread title. But the thing that cannot be argued is that there is no shortage of Muslim migrants doing bad shit to people, especially women, in Europe. I believe that was the spirit of what Trump was speaking of despite the babble bobble bullshit we can expect when his mouth is motoring.
You ate pot and didn't invite me. You're an ass.