Why Was MS-13 Targeted in Trump’s Speech?

This article from the NYT addressed President Trump's speech about illegal immigration. Trump acknowledged MS-13, an extremely violent and ruthless gang, in his speech. MS-13 is by far the most violent and murderous gang in the United States. They were refugees from El Salvador, but spread across the country. Trump brought up one of their more recent assaults on the American people. He used MS-13 as an example of why illegal immigrants can be very dangerous to let in and live here.