BOSTON (CBS) – The MBTA has fired the trolley operator who was at the controls when his trolley crashed into another on the Mattapan Line in late December.

According to The Boston Globe, Leroy H. Mattison, 42, of Malden, was using his phone at the time and was carrying a gun on him.

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Orange Line trolley crash in Dorchester (WBZ-TV)

“The MBTA is extremely disappointed with the alleged conduct of this former trolley operator, who jeopardized the safety of both customers and employees,” the MBTA said in a statement.

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Mattison also could face criminal charges.

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Seventeen people were hurt when the two trolleys collided on the inbound track between Cedar Grove and Butler in Dorchester on December 29.