Teen with a replica gun was robbing a convenience store a day in Dorchester - until detectives spotted him walking into another store, police say

Boston Police report arresting a 15-year-old on charges he robbed three convenience stores on Blue Hill Avenue and Harvard Street in Dorchester - just after he entered a fourth store on Friday.

The teen, too young to have his name released, started at Century Convenience, 766 Blue Hill Ave., on Tuesday around 8:45 p.m. which he robbed at gunpoint, stealing "all the money from the cash register, and several marijuana products," police say.

On Wednesday, the teen walked into the RJ convenience store, 844 Blue Hill Ave. around 6:55 p.m. and stole "money from both cash registers and several marijuana products."

On Thursday, he sauntered into Express Market, 124 Harvard St. around 2:10 p.m. and stole cash.

Police report the teen's streak ended Friday.

Detectives, driving down Harvard Street around 4:35 p.m. to see if anybody might have any additional surveillance video related to the Thursday robbery, spotted somebody walking into the Mini-Central convenience store at 140 Harvard St. who matched the description of the robber: Tall and dressed all in black, including a black ski mask, police say.

The detectives stopped in front of the store, went in and "stopped the suspect inside the store and placed him into handcuffs." After a search, they found a replica handgun matching the one described in the earlier robberies, police say.

The teen was charged with being delinquent for three counts of armed robbery while masked, police say.