Halligan told the students he kept asking himself why this had happened.
But to understand Ryan, and why he took his life, Halligan took the group back to when Ryan was a toddler and having trouble developing language and speech skills.
Special educators helped Ryan, and by the fourth grade, he'd caught up and no longer needed special education services.
The Halligans were aware of the "meanness switch" that seems to turn on in children around fifth grade after their daughter's experiences in middle school.
"Sure enough, the bullying problems started up for Ryan in the fifth grade," Halligan said.
One boy, and eventually his friends, began picking on Ryan for struggling academically and for not being a natural athlete. Ryan wasn't coming home with black eyes. "They were just words," his father said.
The Halligans told him to just ignore the kid and if he didn't get a reaction, he'd stop. Through sixth and most of seventh grade, there were no reports of bullying, no tearful moments.
"Until one night," Halligan said. "This night is so burned into my memory."
It was December 2002 and Halligan came home to find Ryan sitting at the table with his head down. He told his father, "I hate that school. I never want to go back there again."
Ryan asked if his parents could home-school him or if they could move somewhere else, but neither seemed like a real possibility.
It turned out the kid who had picked on Ryan in fifth grade had never let up, and after holding it inside all that time, Ryan finally exploded. He begged his father not to talk to the kid's parents or to anyone at school. He said that would just make it worse.
Ryan came up with a plan. "I want you to teach me how to fight," he told his father. Together they took up Tae Bo kickboxing, and spent many happy hours together watching videos of pitchman Billy Blanks and working out.
"That became our Karate Kid moment," Halligan said.
"If that kid or any of his friends lay a finger on you, you've got my full permission to wail on him. Teach him a lesson just like the Karate Kid," he told his son.
As might be expected, the Halligans got a call from school that Ryan and the bully were fighting and the fight had been broken up. The Halligans found their son walking home from school, and he was pumped, telling his father he got a few good punches in and figured the kid would not bother him again.
Oddly enough, Ryan came home later and told his parents, "I'm actually friends with him now. He's not such a bad guy."
In the summer before his death, Ryan was on the computer all the time, messaging friends constantly.
"On the day my son died we tore the house apart searching for the suicide note - the note that would answer the question why," Halligan said, later learning that suicide notes are not at all common.
But in the course of searching, Halligan found Ryan's AOL account and files of saved chats and got in contact with other children. One girl told Halligan that the bully, who Ryan thought was his friend, had told everyone at school that Ryan was gay. Halligan read the nasty, hurtful comments written to his son.
"My heart started to break into a million pieces all over again," he said.
But Halligan found a folder containing messages between Ryan and a girl. It appeared the two really liked each other. He found out that just before his death, Ryan walked up to this girl and told her, "It's girls like you who make me want to kill myself."
It turns out the girl, who has since appeared with Halligan on TV shows about the topics of bullying and suicide, had tricked Ryan into thinking she liked him and shared his private messages with her friends.
"I can't imagine the pain and the humiliation my son must have felt," Halligan said.
Halligan reached out to the girl, and forgave her, but as for the boy who had hurt Ryan so badly: "I wanted to crush this kid," Halligan said.
The kid admitted he'd started the rumor, and two months later, Halligan found out that this kid and his friends were still picking on Ryan after his death, saying things like, "Ryan was weak. He couldn't handle life, and he was gay."
Instead of beating the snot out of the kid, Halligan sat down with him and his parents. He looked at the boy and said, "You probably have no idea the amount of pain you brought into my son's life."
The kid denied it, and Halligan said, "I refuse to believe that you're that heartless."
The kid started crying and said, "I'm sorry, Mr. Halligan. I'm so sorry."
"I held hate and revenge in my heart for two months, and it nearly killed me," Halligan said.
Halligan took questions from the students and left them with something to consider that he heard from his art teacher: "You can always turn an ink blot into a butterfly. You can always turn a mistake into a lesson learned. You can always turn something bad into something good."