SHENANDOAH, Pennsylvania (CNN) -- Crystal Dillman says she will never understand why a group of teenage boys beat her fiancé to death.



She says she will spend the rest of her life seeking answers -- and justice -- for the man she has lost as she struggles alone to raise her three young children.



"My life is forever destroyed," said Dillman, who was 24 at the time of her fiancé's death. "My family is forever destroyed."



Her fiancé, Luis Ramirez, an undocumented Mexican immigrant, was walking down the street in Shenandoah, Pennsylvania, on July 12, 2008, with Dillman's half-sister, who is white.



A fight broke out between him and a group of white high school football players. He died from his injuries two days later, leaving a small community stunned at the brutality of the crime.



A central issue in the case is race in a town with a reputation for being an ethnic melting pot.



Witness Eileen Burke said she heard the group call Ramirez a "spic."



One of the boys who was charged as a juvenile, Brian Scully, admitted telling Ramirez to "go home, you Mexican motherf---er." Residents speak out about the crime, racial overtones



Scully was charged with ethnic intimidation.



Another teen pleaded guilty to federal civil rights violations in a plea deal. But two teens who faced a local jury were acquitted of charges of ethnic intimidation.



Dillman doesn't doubt that the attack was racially motivated.



"They said some racist remarks to him," Dillman said of the teens. "Truly, in my heart, I believe they beat him up because he was Latino."



Many in Shenandoah deny that race played a role and say it was just a street fight gone wrong.



The young men involved were ordinary high school students -- good kids, according to their families, friends and coaches. Shenandoah resident interrupts CNN interview



It took almost two weeks for arrests to be made. But on July 25, Colin J. Walsh, 17, and Brandon J. Piekarsky, 16, were charged as adults with homicide and ethnic intimidation.



Derrick M. Donchak, 18, was charged as an adult with aggravated assault and ethnic intimidation.



Walsh, who admitted throwing a punch that left Ramirez unconscious, got straight A's in school and ran track. His father says he was never a troublemaker. See photos of key figures in the case



But how do ordinary kids get caught up in such a brutal incident?



Experts say everyone has biases, and violent instincts are common, especially in young adults.



Young offenders



"Hate is part of our culture," said Jack Levin of the Brudnick Center on Violence at Northeastern University.



"It transcends generations, it's widely shared, and it's learned from an early age," Levin said. "Even otherwise decent, honorable people can be pulled into it."



Jack McDevitt of Northeastern University's Institute on Race and Justice said, "We all carry around biases with us, and it's not the extraordinary monster that decides to act on it. Generally speaking, it's someone more like us and our children than a member of the [Ku Klux] Klan."



Research conducted by both Levin and McDevitt shows that there are three major types of hate crime offenders:



• "Thrill seekers" who look for excitement and power in attacking a person they perceive as different.



• "Retaliators" who seek revenge for a real or perceived crime against someone similar to the attacker.



• "Defenders" who are trying to protect their neighborhood or way of life.



Perhaps the most expected type is also the rarest: an offender who may be a member of a group like the KKK and has a deep-seated hatred of a specific ethnic group.



"Hate criminals, most of them young men, believe they are carrying out the fervent, unspoken wishes of their communities," said Mark Potok, director of the Southern Poverty Law Center's Intelligence Report.



McDevitt says offenders
Where was he killed What was the reason he was beaten? What is his fiancee quoted as saying? who was killed A small town is stunned by the death of who? What did the expert say?
Shenandoah, Pennsylvania, Mexican "My family is forever destroyed." Luis Ramirez, Luis Ramirez, everyone has biases, and violent instincts are common, especially in young adults.
question: Where was he killed, answer: Shenandoah, Pennsylvania, | question: What was the reason he was beaten?, answer: Mexican | question: What is his fiancee quoted as saying?, answer: "My family is forever destroyed." | question: who was killed, answer: Luis Ramirez, | question: A small town is stunned by the death of who?, answer: Luis Ramirez, | question: What did the expert say?, answer: everyone has biases, and violent instincts are common, especially in young adults.