EVANSTON, Ill. (CBS) – Police are searching for the robber who held up a jewelry store in the heart of downtown Evanston Tuesday morning, and tied up the clerk.

At 11:15 a.m. Tuesday, Evanston police were sent to Diadem Jewelers, at 1613 Sherman Ave. in Evanston, following an armed robbery.

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The victim told police he had opened the store was open for the day when the robber entered, took out a handgun and announced a robbery.

The robber then tied up the clerk’s hands with flexible plastic bindings, and took jewelry from the display cases. He stashed the jewelry away in a gym bag and backpack, then fled through the back door and ran off, police said.

A short time afterward, a passerby looked into the store and saw the clerk still tied up. That passerby called police.

The victim describes the robber as an African-American man of about 30, standing 6 feet tall and weighing 250 pounds, wearing a baseball cap, sunglasses, a scarf, a black leather coat, dark jeans and dark gym shoes.

As of early Tuesday afternoon, Evanston police continued their investigation. They had not yet determined what specific pieces of jewelry were missing.