President Donald Trump condemned a terrorist attack in Paris, pointing to the “sickness and hatred” that motivated it.

“So sad to see the Terror Attack in Paris. At some point countries will have to open their eyes & see what is really going on,” he wrote on Twitter on Sunday. “This kind of sickness & hatred is not compatible with a loving, peaceful, & successful country!”

The alleged attacker, Khamzat Azimov, was a French citizen born in Chechnya who stabbed five people with a knife before being shot and killed by police. One person died from his stabbing wounds. Azimov, age 20, was inspired by the Islamic State and was on a terrorist watch list before the attack.

Trump called for a change in the international approach to terrorism.

“Changes to our thought process on terror must be made,” he wrote.

The White House issued a statement after the attack:

The United States strongly condemns yesterday’s terrorist attack in Paris. Our thoughts and prayers are with the victims and their families. We stand in solidarity with the French people and their government against this vicious act of terrorism, and pledge any assistance needed. Acts like this only strengthen the resolve of the global coalition to defeat ISIS and drive it out of existence.