Alleged robber dropped his cellphone, leaving crucial clue, authorities say

A Winthrop man made a crucial mistake when he dropped his cellphone during an armed robbery in Boston, leaving a clue that helped police track him down and connect him to several other crimes, authorities said.

Dennis Stack, 41, was arraigned Tuesday in Charlestown District Court on a charge of armed robbery of a Dunkin’ Donuts in December. His bail was set at $15,000, and he is slated to return to court March 24, the Suffolk district attorney’s office said in a statement.

He also faces charges in three other December robberies in Suffolk County, prosecutors said.

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Boston police responded to reports of an armed robbery at a Dunkin’ Donuts on Cambridge Street at about 12 p.m. on Dec. 10. Witnesses said Stack ordered the clerk to give him all the store’s gift cards and cash, and threatened he was armed and would kill everyone in the store.

Stack allegedly tried to climb over the counter, but was tackled from behind by another customer. Stack dropped a tire iron and a white iPhone during the ensuing struggle, prosecutors said.

Stack fled in a getaway car with $65 cash from the register.

When police arrived, they saw that the cellphone had received several calls and text messages addressed to “Dennis.” Officers called one of those numbers, and the person who answered identified Stack as the phone’s owner, prosecutors said.

Officers also compared the store’s surveillance footage to other photos of Stack to identify him as the armed robber, prosecutors said.