Outgoing Rep. Ryan Costello (R-Pa.) blasted President Donald Trump’s threat Friday to shut down the southern border as an “angry eighth-grader’s tweet.”

Trump issued the warning on Twitter, saying if he didn’t get his way on funding for his wall, he would simply close down the Mexican border.

“This struck me as like an angry eighth-grader’s tweet,” Costello said on CNN. “I don’t really know how to make sense of it because I don’t think he can do this even if he wanted to. It probably violates NAFTA. I don’t think he’ll have much if any support in Congress. Nor do I think logistically he’d be able to implement it.

“And when you start throwing out vacuous threats like this, people stop taking you seriously in terms of how you go about negotiating.”

Costello, who announced in May that he would not run for re-election, tweeted earlier this month that Trump’s political pressure on the Democrats just as they are about to take control of the House was “toddler logic.”

While Trump is blaming the Democrats for the ongoing government shutdown, he was the one who refused to sign a temporary spending measure until he gets billions of dollars for his border wall, a signature campaign promise. He said earlier this month he would be “proud” to shut down the government for “border security.”

“Remember, the president said that this is his shutdown,” Costello said. Now it’s not “clear on what amount of money he needs in order to sign a funding bill,” he added. “The ball’s in the president’s court, and we have no clarity on what he’s willing to accept or what he might sign.”

Check out the interview in the clip above.