Eric Trump has said he was spat on by an employee at a cocktail bar in Chicago, insisting the alleged incident shows "we are winning".
The US Secret Service, which offers protection to Donald Trump's children, reportedly took the employee at the upmarket Aviary into custody before letting her go after the president's middle son declined to press charges.
“It was purely a disgusting act by somebody who clearly has emotional problems. For a party that preaches tolerance, this once again demonstrates they have very little civility," Mr Trump told far-right website Breitbart, in reference to the Democratic Party.
"When somebody is sick enough to resort to spitting on someone, it just emphasises a sickness and desperation and the fact that we’re winning.”
A local reporter for NBC5 Chicago, Mary Ann Ahern, said the incident occurred around 8.30pm on Tuesday night. She shared a photo of police officers outside the bar in Fulton Market.
Anthony Guglielmi, a spokesman for the Chicago police department, confirmed officers had attended the scene.
According to Breitbart – one of the Trump family's preferred publications – the waitress approached the businessman and spat in his face. She "murmured inaudibly something that sounded like it was anti-Trump", according to a Breitbart source.
She was reportedly put in handcuffs before later being released from custody.
In a statement, an Aviary spokesperson said the bar was "just beginning to learn the details" of the "unfortunate incidence" involving Mr Trump.
"What is certain is this: no customer should ever be spit upon," the spokesperson said, adding their its employee had been placed immediately on leave.
"More broadly, the online discussion about the incident is troubling. Hundreds of people are calling for the demise of our business, threatening our employees, and posting fake reviews ... they are wrong to do so based on the actions of a lone individual."
"So too, however, are those people wrong who are praising this as an act of civil disobedience. We have voices and the means to be heard. A degrading act lowers the tenor of debate. To some it might feel good, but it is unlikely to serve any larger purpose.
"We hope this incident can, at least, serve to illuminate the current absurdity of the discourse in our politics. As fellow Americans and citizens, we should all aim higher."
Chicago police have been contacted for comment.
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