Story highlights "You have to be kidding me?!" Trump Jr. tweeted

Khan and Trump had sharp words for each other during the campaign

This story has been updated to reflect the latest number of fatalities from London Metropolitan Police.

Washington (CNN) President Trump's son is criticizing the mayor of London in the immediate aftermath of an attack in the city that killed four and wounded about 40 on the grounds of the UK Parliament.

Trump's son, Donald Trump Jr., manages the Trump Organization and has no role in the White House, but he remains an occasional surrogate for his father. The younger Trump also occasionally calls out the President's political opponents on Twitter, the venue he chose Wednesday to weigh in on the incident in Britain.

You have to be kidding me?!: Terror attacks are part of living in big city, says London Mayor Sadiq Khan https://t.co/uSm2pwRTjO — Donald Trump Jr. (@DonaldJTrumpJr) March 22, 2017

"You have to be kidding me?!" Trump Jr. tweeted, as he shared an article from The Independent, and paraphrased its headline as: "Terror attacks are part of living in big city, says London Mayor Sadiq Khan"

The article, published in September 2016 , featured Khan's reaction to a bombing in the Chelsea neighborhood of New York. In it, Khan said that preparedness for terror attacks is "part and parcel of living in a big city," and asked Londoners to be correspondingly "vigilant."

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