The FBI and Portland police are offering a $10,000 reward to anyone who can help convict those responsible for killing Frank A. Williams III in 2008.

The announcement came Wednesday on the 15th anniversary of Williams’ death.

The 37-year-old died from multiple stab wounds at Maine Medical Center. Witnesses told police at the time that a crowd had gathered around the soccer field at Kennedy Park early that morning, drawn by the sound of an escalating conflict. The crowd scattered when three men chased Williams, stabbing him before he climbed through a hole in a fence along the field.

Police quickly launched a search for the three men, who they said apparently knew the victim. Officers said at the time that they had leads on the attackers’ identities.

“We will pursue justice for Mr. Williams and his family, no matter how long it takes, and we hope this reward will incentivize anyone with information to come forward,” Christopher DiMenna, acting special agent in charge of the FBI Boston Division, said in a statement.

Portland Police Chief Mark Duboi thanked the FBI for their involvement.

“This might get my detectives the information that they need to identify those responsible and bring closure to the Williams family,” he said in a statement. “In most homicides there is someone that has that crucial piece of information that might help investigators corroborate evidence they already know or direct them to a new lead.”

Williams’ family and former girlfriend told the Portland Press Herald in 2008 that he had battled drug use, which police said might have played a role in the attack. They also said Williams had been involved in several assaults over drugs.

Williams worked on commercial fishing boats in Portland and was not homeless, his father has said. When Williams died he had a 1-year-old daughter in Biddeford and a 14-year-old son in the Midcoast area.

In a statement issued through Portland police Wednesday, Williams’ father said “I am 71 years old and I would love to see someone held responsible for my son Frankie’s death. It has been almost 15 years and it is not fair.”

Anyone with information is asked to call Portland police at 207-405-0929 or the FBI at 1-800-CALL-FBI. Tips can also be submitted online.