BOSTON (CBS) – The operator of a runaway Red Line train cut corners and violated safety procedures that could have had “catastrophic” consequences, according to the final investigative report released Tuesday.

About 50 passengers endured a harrowing nine-minute ride on the morning of December 10. The inbound train traveled through four stations before it was brought to a halt just past North Quincy Station, when crews powered down the third rail.

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Read: Full MassDOT Report On Unmanned Red Line Train

Operator error had been the primary focus of the initial investigation into the cause of the incident.

“The Department concurs with the probable cause findings specifically, that the operator violated a number of critical MBTA safety rules which lead to the unattended train event,” the 73-page report said.

The operator, 53-year-old David Vazquez, wrapped a rubber microphone cord around an accelerator control on the train. According to the report, Vazquez manipulated the control while he was putting on gloves.

Cord wrapped around runaway Red Line train's controls (Image from MassDOT)

Cord wrapped around runaway Red Line train’s controls (Image from MassDOT)

“It was operator error, my fault,” Vazquez apparently said shortly after the incident.

When the 25-year veteran MBTA employee got off the train to bypass a persistent signal problem, the report states, Vazquez did not remove the cord around the dead-man feature and did not set the hand brake.

After flipping the bypass switch, the train shot forward. Vazquez sustained an injury to his leg. However, none of the passengers were hurt.

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Cord wrapped around controls of runaway Red Line train (Image from MassDOT)

Cord wrapped around controls of runaway Red Line train (Image from MassDOT)

The MBTA fired Vazquez shortly after the high-profile incident. According to disciplinary documents included in the report, agency leaders concluded, “Your actions and negligence could have been catastrophic in nature.”

The report revealed Vazquez had five safety violations prior to the runaway incident.

Investigators also reviewed similar runaway train incidents previously reported by the I-Team, and discussed possible changes to avoid any future problems.

The MBTA is looking at the costs of adding surveillance cameras to the cabs of trains, so supervisors can make sure operators are following safety procedures. All new cars being built for Orange and Red Lines will be delivered with that technology feature.

Engineers are also studying whether certain aspects of the train design can be reconfigured to prevent tampering. Another possibility would move the “bypass” switch inside the cab, so drivers would not have to exit the train.

“Within a week of the incident, the MBTA acted quickly, implementing new procedures which require a supervisor to be present when a train operator is granted permission to ‘bypass’ a faulty signal,” MBTA General Manager Frank DePaola said in a written statement.

“The MBTA also issued a special order to all train operators, reinforcing the policies against tampering with safety equipment.”

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Ryan Kath can be reached at rkath@cbs.com. You can follow him on Twitter or connect on Facebook.