BOSTON (CBS) – Transit Police have filed charges against a Green Line trolley driver involved in a crash in July. Owen Turner is facing two gross negligence charges, one of which is a felony.

Transit Police said Turner initially told officers he had no memory of the crash on July 30. The next day, he told police he may have fallen asleep.

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A preliminary report by the NTSB found Turner put the train into full power right before it crashed into another trolley near Boston University. More than 20 people were treated for injuries.

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Turner was placed on leave after the crash.

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“The MBTA appreciates the work of Transit Police investigators and the Suffolk County District Attorney’s office,” an MBTA spokesperson said. “The MBTA is taking the steps necessary to end the employment of the individual involved in the collision.”