The President's son quoted an interview Mr Khan did with the Evening Standard last September, following an explosion in the Chelsea district of NY that left 29 people injured.
However, it is Khan's lack of response and previous statements of "terrorism being part and parcel to big city living" that has some questioning the mayor's commitment to safety and anti-terrorism policy.
Some 20 people were injured when the attacker drove a vehicle into pedestrians on Westminster Bridge and crashed into railings outside the Palace of Westminster on Wednesday afternoon.
News about Wednesday's attack in London was still filtering in at the time of this post's publication.
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The pair were also caught kissing in Cummins' classroom around two months ago, according to documents obtained by WKRN News 2 . The last person to have talked with the girl before her disappearance was her friend who dropped her off at the restaurant.
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A Greek police source on Monday said the eight additional packages had been scanned and "found to contain a similar mechanism". The group initially carried out arson attacks but turned to bombings in 2009.
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Also making the very Scandinavian top 5 are Iceland and Finland, with Switzerland being the odd one out by occupying fourth place. Everything from poor life expectancy and job dissatisfaction to lack of social support and trust in government and business.
Mayor of London Sadiq Khan offered his thanks to the police and emergency services, and said they had showed "tremendous bravery" during today's terrorist attack at Westminster.
"It is a reality I'm afraid that London, New York, other major cities around the world have got to be prepared for these sorts of things", Khan told the Evening Standard.
The former Ukip leader also used his time to proclaim sometimes controversial protocols - such as Donald Trump's so-called Muslim ban - were in place to keep people safe.
Donald Trump Jr's choice to share a seven month old article, seemingly without reading it or pointing out that it was an old quote, was received with disbelief and overwhelming denigration.
"Nothing is more important to me than keeping Londoners safe", he said.