Hawaii police are seeking to identify the armed thief who pulled off a brazen $1 million jewelry store stick-up on Halloween in a black mask and full-length black robe.

Maui police on Saturday released surveillance images of the armed thief who robbed Greenleaf Diamonds of three diamonds at lunchtime on Oct. 31. They announced a $50,000 reward for information that helps nab the crook.

“The business was vacant of customers when the unknown male entered (and) brandished a black Glock-like, semi-automatic looking pistol,” police said in a Facebook post.

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Police in Maui, Hawaii, is seeking to identify the armed thief who held up a jewelry store on Halloween in a mask and robe and made off with three diamonds worth $1 million. (Maui Police Department)

“Once the male brandished the weapon he demanded three items from the display case which contained multiple pieces of other jewelry,” they said.

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The robber stole two diamond rings valued at $240,000 and $450,000 and a pair of diamond stud earrings valued at $378,000, according to police.

They said he had on the robe, the mask, black gloves, and black Nike shoes.

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Police said the reward had been posted by the jeweler's insurer.