Morris County Sheriff James Gannon says the reward has increased to $50,000 for information on an unsolved murder case of a teen killed 40 years ago.

The victim's family members gathered over the weekend to plead with the public for help in the investigation.

The Morris County Prosecutor's Office says Christopher Thomas was outside the Rockaway Townsquare mall with his girlfriend on Oct. 1, 1982. The prosecutor’s office says a person described as a man in his early 20s approached and shot him.

Officials say the man who shot Thomas had a thin build, a slight dark mustache, and shoulder-length dark hair parted in the middle. He wore a blue coat and mirrored glasses. The suspect may have been wearing a costume from the movie "Rocky Horror Picture Show," which was showing at the theater.

Investigators don’t believe Thomas was targeted in the apparent random attack. They added the individual who shot him is likely still living in the Morris County community.

"Everyone has a Christopher Thomas in their class," his brother, Mark Thomas says. "He was the best athlete. He was the straight-A student, and he was literally everyone's friend. I truly believe in my heart that there is someone, somewhere, with additional information about those events and all I can ask is that person would come forward with that information."

Thomas attended Morris Catholic High School in Denville.

Anyone with information is urged to contact authorities at 973-COP-CALL or visit CopCall.org