A $50,000 reward is being offered for information leading to the arrest and conviction of those responsible for a $1 million robbery at a Lahaina jewelry store on Halloween, Maui police said Friday.

The robbery occurred at about 12:15 p.m. at Greenleaf Diamonds, 730 Front St., when a masked man entered and brandished a Glock-like, semi-automatic-looking pistol, police said.

The robber demanded three items from a display case that contained multiple other pieces of jewelry.

The three stolen items were a loose GIA 10.10-carat pink diamond valued at $240,000, 14K white gold 20.20-carat diamond stud earrings valued at $378,000, and a platinum 5.06-carat fancy light pink GIA diamond valued at $450,000. The value of the three pieces of stolen jewelry totaled about $1.07 million.

Jewelers Mutual Insurance Co. is offering a $50,000 reward for information leading to a conviction in the robbery. The insurance company will also pay 10% of the cost of any merchandise recovered through the use of provided information.

Police said the robber was dressed in a full-length black gown, with black gloves and a black mask. He wore black Nike shoes with a white swoosh and white soles.

Anyone with information on the heist is asked to email detective Matthew Brown at matthew.brown@mpd.net.