COLD CASE UPDATE: SIX-FIGURE REWARD OFFERED IN COLUMBINE HS SWEETHEARTS' MURDER. DO YOU KNOW WHO KILLED THEM?

They were high school sweethearts who survived one of the most unspeakable tragedies in American history. A year later, they were found murdered.

Today, their suspect remains on the lam and officials hope a new six-figure reward can help close the decades-old cold case. 

Stephanie Hart-Grizzell, 16, and Nick Kunselman, 15, were students at Columbine High School in Colorado. The two met in middle school and became friends, later developing into a romantic relationship. 

In 1999, two classmates opened fire inside the Colorado High School killing 12 students and a teacher. The couple survived the attack, but a year later on Valentine’s Day 2000 were found dead in Littleton, Colorado. 

The two were shot and killed inside a Subway shop a few blocks from Columbine High School. Kunselman was an employee and Hart-Grizzell was waiting for him to finish work. 

“The reward in this case is now up to $100,000. What this shows is people still care, people want answers, people want justice for Nick and Stephanie and the entire community,” Sarah Johnston with Metro Denver Crime Stoppers told Fox 31 in Denver.

The reward recently increased from $12,000 to $100,000 to mark the anniversary of the killings. It is the largest reward the Metro Denver County Crime Stoppers has ever offered. 

Information regarding the Valentine’s Day double-homicide can be reported to Metro Denver Crime Stoppers by calling (720)913-7867 or (720)913-STOP. Tips can also be submitted online.

“This would be the time for us to go all in and put an amount there that would get the attention of people. Hopefully it gets folks taking and maybe it gets to the person who has the information we need,”  Jefferson County Sheriff Jeff Shrader told FOX31

Early on in the investigation, a possible description of the suspect was given to investigators. According to The Denver Channel, the suspect was described as a white male between 16 to 20 years old and around 150-170 pounds with blonde hair. Unfortunately, these leads went cold. 

As reported by The Denver Channel, Kelly Grizzell, Stephanie’s mother, stated, “although they had just gone through the tragedy at the high school, they were coming through it so good, and they were so happy.”