Less than a year after the Columbine High School massacre, the two were mysteriously gunned down at the restaurant on Valentine's Day.

LITTLETON, Colo. — Nick Kunselman and Stephanie Hart-Grizzell loved each other more than their families thought kids could.

The two high school sweethearts were drawn together by a love of arts and music.

Then, on Feb. 14, 2000 -- exactly 19 years ago -- the two were mysteriously gunned down at a Subway sandwich shop where Kunselman worked. Hart-Grizzell was at the shop waiting for Kunselman to get off work.

Hart was 16 and Kunselman was 15 at the times of their death.

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The shop, at 6768 W. Coalmine Ave. in Littleton, was a few blocks south of Columbine High School, and it happened less than a year after the attack that occurred there on April 20, 1999.

One of Kunselman's co-workers drove past the restaurant and noticed the lights still on inside. When the employee entered the restaurant, they found Hart's and Kunselman's bodies behind the counter.

Investigators determined both had been shot by an unknown intruder.

The murders of Kunselman and Hart-Grizzell remain unsolved.

The employee who found them shot also saw a person exit out of the back of the shop: a man who was about 5 feet, 8 inches tall, white and had blonde hair.

Anyone with information about the crime is asked to contact Metro Denver Crime Stoppers at 720-913-7867.

An award of $2,000 is being offered.