Both tweets attacked David Hogg, one of the students who documented the horror felt by his peers during the Parkland school shooting, and who has since been outspoken in his call for lawmakers and politicians to take action against guns.
"The FBI are some of the hardest-working individuals I've ever seen in my life," Hogg said.
In an interview with NBC, Hogg also urged Trump to take gun reform action, saying, "You're the president. You're supposed to bring this nation together, not divide us. How dare you? Children are dying, and their blood is on your hands because of that. Please take action. Stop going on vacation in Mar-a-Lago. Take action. Work with Congress. Your party controls both the House and Senate. Take action, get some bills passed, and for God's sake, let's save some lives."
Trump Jr. liked a tweet from conservative TV show host Graham Ledger that linked to a story by far-right, pro-Trump website, Gateway Pundit, suggesting that Hogg's father had "coached" his son in propagating "anti-Trump rhetoric and anti-gun legislation."
Trump Jr. also liked a tweet linking to a story by True Pundit — a far-right website that has published several false stories — which referred to Hogg as "the kid who has been running his mouth about how Donald Trump and the GOP are teaming to help murder high school kids by upholding the Second Amendment."
The piece blamed "the Deep State media" for giving Hogg a platform and appeared to express doubt that he was a survivor of the shooting.
Hogg told BuzzFeed News on Tuesday that Trump Jr.'s peddling of conspiracy theories was "immature, rude, and inhuman."
"I just think it's a testament to the sick immaturity and broken state of our government when these people feel the need to pedal conspiracy theories about people that were in a school shooting where 17 people died and it just makes me sick," Hogg told BuzzFeed News via text. "It's immature, rude, and inhuman for these people to destroy the people trying to prevent the death of the future of America because they won't," he said.
One of his classmates also pointed out on Twitter that the idea of Hogg being a professional actor was, well, laughable.
BuzzFeed News has reached out to Trump Jr. and the White House for comment.