Joselyn Martinez was just 9 when her father, Jose, was shot and killed outside of the family's Dominican restaurant in New York City in 1986.
His killer was never caught.
Now, 27 years later, Joselyn may have helped solve her father's murder by using online background checks that she gave to the New York police department.
"They shot him outside. My father was unarmed," Martinez told ABC News. "How do you just forget it?"
Police identified a suspect in the aftermath of the shooting, a 16-year-old named Justo Santos who escaped to the Dominican Republic during the investigation and was never tracked down.
New York Police Commissioner Ray Kelly said that the department closed the case mistakenly when Santos was arrested and imprisoned in the Dominican Republic.
"In fact he was arrested, but it turns out he was only in jail for a couple of years," Kelly said.
Martinez spent years looking for information on Santos, and eventually paid money to websites that perform background searches on a person with the same name and birthday as the alleged killer. The websites said that Santos was living in Florida.
"I thought it isn't even real, because this can't be," Martinez said.
Martinez gave the information to New York police, who last Thursday arrested Santos.
"I applaud her," Kelly said. "Obviously she made a concerted effort and it paid off."
Santos has confessed to the crime, according to police. He appeared in court in Miami on Tuesday and will be extradited to New York to face murder chages.
Martinez said the arrest will allow her and her family to have peace.
"We know it's not going to bring the person back, but this is for my dad," Martinez said.