Rep. Filemon Vela (D-Texas) lashed out at President Donald Trump for using Friday’s deadly mass shooting at an Egyptian mosque to keep up his push for construction of a wall along the U.S.-Mexico border.

“What an idiot,” Vela tweeted Sunday in response to a Washington Post piece analyzing Trump’s suggestion that a border wall would effectively stop Muslim extremists from entering the United States.

Vela, an outspoken Trump critic, questioned whether the president “foolishly” believed such a wall could have prevented the 9/11 attacks, as well as the wave of mass shootings plaguing the country, including the ones in Las Vegas last month and at a Texas church earlier this month.

What an idiot... Does @realDonaldTrump foolishly think a border wall would have prevented 9/11, Charleston, San Bernardino, Orlando, Las Vegas, and Sutherland Springs? — US Rep. Filemon Vela (@RepFilemonVela) November 26, 2017

Some details remain unclear over Friday’s attack in Egypt, which left at least 305 dead in the Sinai region. No group has claimed responsibility, though gunmen carried the black flag of the Islamic State during the attack. Trump almost immediately used the attack to peddle his border wall and tighter immigration policies.

Will be calling the President of Egypt in a short while to discuss the tragic terrorist attack, with so much loss of life. We have to get TOUGHER AND SMARTER than ever before, and we will. Need the WALL, need the BAN! God bless the people of Egypt. — Donald J. Trump (@realDonaldTrump) November 24, 2017

Throughout his 2016 presidential campaign, Trump promised his supporters “a big, beautiful wall” if elected. But in the more than 10 months since taking office, Trump has failed to make any significant progress on it.

There’s little evidence to suggest terrorists are crossing into the U.S. using the southwest border. Only “a handful” of people with ties to Islamic terrorist groups have ever been caught attempting to enter the U.S. from there, the Post reported Saturday.

In most U.S. mass shootings, the gunmen are white, male U.S. citizens.