The statement about the celebrations was in paragraph 15.
From Rooster's link
"In Jersey City, within hours of two jetliners' plowing into the World Trade Center, law enforcement authoritiesdetained and questioned a number of people who were allegedly seen celebr ating the attacks and holdingtailgate-style parties on rooftops while they watched the devastation on the other side of the river."
There were some Israelis detained for about 2 months. Those I think they pulled out of an Urban Moving Systems van. Then they were let go and appeared on Israeli tv speaking Hebrew.
I don't know if it was that van or another bigger truck, it is on Google images and youtube. It had a mural painted on the side with the twin towers and an airplane. Very strange.
Be that as it may, it would have been mostly Arabs celebrating. And WAPO owes Trump an apology, but he won't get it. It's another way they trick the public. Put it out there whether true or not. Then they get away with the subterfuge or um lie because the public attention span is short and they don't question. Trump was telling the truth about celebrations.