Musk, who owns the platform, put up the post after a man suspected of planning to assassinate former President Donald Trump at his golf course in West Palm Beach was arrested on Sunday.
A Trump supporter and the CEO of Tesla, Musk wrote on Sunday: "And no one is even trying to assassinate Biden/Kamala," a post he ended with an emoji of a face with a raised eyebrow.
Well, one lesson I've learned is that just because I say something to a group and they laugh doesn't mean it's going to be all that hilarious as a post on �— Elon Musk (@elonmusk) September 16, 2024
He was quickly criticised by X users from the left and right, who said they were concerned his words to his nearly 200 million X followers could incite violence against Biden and Harris.
Musk deleted the post but not before the Secret Service, tasked with protecting current and former presidents, vice presidents and other notable officials, took notice.
"The Secret Service is aware of the social media post made by Elon Musk and as a matter of practice, we do not comment on matters involving protective intelligence," a spokesperson told Reuters on Monday.
"We can say, however, that the Secret Service investigates all threats related to our protectees."
The spokesperson declined to specify whether the agency had reached out to Musk, who seemed to suggest in follow-up posts that he had been making a joke.
"Well, one lesson I've learned is that just because I say something to a group and they laugh doesn't mean it's going to be all that hilarious as a post on X," he wrote.
"Turns out that jokes are WAY less funny if people don't know the context and the delivery is plain text."
Harris, a Democrat running against the Republican Trump in the 2024 election, and Biden both issued statements on Sunday night expressing relief that Trump had not been harmed.
