BRENTWOOD, N.Y. -- The president came to Long Island to talk to law enforcement officers about a gang known as MS-13 that he says has neighborhoods under siege.

"They like to knife them and cut them and let them die slowly, because that way its more painful, and they enjoy watching that, because they are animals," President Trump said.

The venue, Suffolk County Community College, was chosen because there have been 17 gang-related murders near the school over the past 18 months.

"It is the policy of this administration to dismantle, decimate and eradicate MS-13," Mr. Trump said Friday. "We will find you, arrest you, jail you and we will deport you."

President Trump spoke to Suffolk County Police officers on July 28, 2017. CBS News

Mr. Trump even had words of advice to law enforcement on how to handle these arrests.

"I said please don't be too nice -- like when you guys put somebody in the car and you're protecting their head ... I said you can take the hand away, OK?" Mr. Trump said.

Outside the college, about 400 protesters were kept far away from the president.

That's where we found Raj and Sommer Chetty with their kids. They were skeptical about the president's motives.

"Yes, MS-13 is a blight, as gangs are anywhere," Raj said. "But it's a pawn. It's a dog whistle."

"It's a way to demonize a whole group of people, a whole group of immigrants, a whole group that doesn't necessarily look the same, speak the same," Sommer said.

Late Friday afternoon, the Suffolk County Police Department issued a statement saying "we do not and will not tolerate roughing up prisoners." Meanwhile, the president is pushing Congress for more funds for his immigration policies.