A suspected arsonist who was 12 when he allegedly set ablaze a college library in which a firefighter was killed more than three decades ago has been charged, Washington authorities said Thursday. 

Everett firefighter Gary Parks, 48, died on Feb. 16, 1987 while responding to a fire at Everett Community College, the Everett Police Department said. Parks, an 18-year-veteran of the fire department, became separated from five other firefighters while battling the blaze in the college library before he became trapped and died. 

The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) assisted local authorities with processing the scene of the fire and determined it was intentionally set. 

A man was charged this week in the alleged arson at Everett Community College more than three decades ago that killed a responding firefighter. (Everett Police Department)

Several underage boys were thought to have entered the library through an open window and purposefully started the fire, police said. Investigators never gave up and periodically revisited the case over the years. After multiple interviews with Elmer Nash Jr., 46, he admitted to starting the blaze. 

"Eventually, Nash confessed to starting the fatal fire and expressed concern that he hadn’t intended to hurt anyone," police said. 

He plesded guilty to murder charges Thursday. 

CLICK HERE TO GET THE FOX NEWS APP

"After 34 years, the City of Everett will finally see someone held accountable for the loss of our Firefighter Gary Parks, who died in the service of our community," said Everett Mayor Cassie Franklin. "I commend our city teams for working tirelessly to crack the case and continue towards resolution in this tragic event."

In a statement, Everett Fire Chief Dave DeMarco said the "generation of Everett Firefighters who worked with Gary have retired, but the memory of his loss is woven into the culture of the Everett Fire Department."