By SELIM ALGAR, KIERAN CROWLEY and SEAN GARDINER

Seven Long Island teens were on a hateful mission to hunt down Mexican immigrants when they surrounded, beat and fatally stabbed a hardworking Ecuadorian man, a prosecutor charged yesterday.

"This was not some high-school prank," Assistant Suffolk DA Nancy Clifford said at yesterday's Central Islip arraignment of the suspects, who included a high-school lacrosse star.

"This was a well-thought-out crime specifically targeting Hispanics.

"In their own words," Clifford said, they decided beforehand, " 'Let's go find some Mexicans to f- - - up.' "

Suspects Jeffrey Conroy, Kevin Shea, José Pacheco, Anthony Hartford, Nick Hausch and Jordan Dasch, all 17, and Chris Overton, 16, are accused of attacking Marcello Lucero, 37, near the Patchogue LIRR station Saturday night.

Clifford said the youths - who attend Patchogue-Medford HS - were intent on doing some "beaner jumping," using a derogatory term for Mexican-Americans.

Police sources said the group is suspected in at least one other hate crime that took place last month in the area, where an influx of immigrants seeking work has created violent tensions with locals. But authorities couldn't pursue charges because the Hispanic victim was too frightened to testify, sources said.

Just before midnight Saturday, Lucero and a pal were walking to another friend's home when the teens piled out of an SUV yelling racial epithets.

As his friend ran, Lucero pulled his leather belt from his waist to defend himself. But he was no match for the thugs. Shea later boasted, " 'I punched him, I got him good. I saw blood coming down,' " police sources said.

At one point, Lucero managed to scramble to his feet. That's when Conroy, a lacrosse and wrestling star who sources said has a swastika tattoo on his thigh, allegedly stabbed him in the chest.

Joselo Lucero called his older brother a "simple guy" who worked for a dry cleaner. A bachelor, he came to the United States 16 years ago.

"The dreams of USA, sometimes it's not worth it because you pay with your life," the brother said. All the suspects but Conroy were ordered held on high bail after pleading not guilty to charges of gang assault as a hate crime. Conroy, who was also charged with manslaughter as a hate crime, was remanded without bail, pleading not guilty to all counts.

While several classmates said the group was known to target Hispanics, student Eric Maldonado, 17, said he didn't think the attacks were racially motivated because Pacheco is half-Hispanic.