Apple CEO Tim Cook on Tuesday criticized the Trump administration for its “heartbreaking” and “inhumane” policy of separating immigrant children from their parents at the U.S. border with Mexico.

“It’s heartbreaking to see the images and hear the sounds of the kids. Kids are the most vulnerable people in any society. I think that what’s happening is inhumane, it needs to stop,” Cook told The Irish Times.

The Department of Health and Human services has 11,785 minors in its care, NBC News reported Monday, citing a department official. The number of migrant children in HHS custody has climbed as a result of the administration’s “zero tolerance” policy on illegal border crossing.

President Donald Trump has publicly defended the controversial policy.

@realDonaldTrump: We must always arrest people coming into our Country illegally. Of the 12,000 children, 10,000 are being sent by their parents on a very dangerous trip, and only 2000 are with their parents, many of whom have tried to enter our Country illegally on numerous occasions.

Speaking in Dublin on Tuesday, Cook criticized the policy and said Apple will be a “constructive voice” in the situation.

“I’m personally a big believer in the way to be a good citizen is to participate, is to try to advocate your point of view, not to just sit on the sideline and yell or complain,” Cook told the Irish Times.

“That will be the approach we will take here. This one in particular is just heartbreaking and tragic.”