How did a young girl end up getting her arm stuck in a door on the Green Line?

The MBTA is investigating after the girl – identified in news reports as 8-year-old Faith Felt – reportedly had a pair of B Line doors close on her right arm while stepping off the trolley ahead of her mother at Harvard Avenue about 8:30 p.m. on Monday.

Felt was later treated for a sprained wrist at a nearby hospital.

The operator, who has not been identified, has been placed on leave while the investigation is underway. He passed a “fitness for duty” test after the incident, according to T records.

Accounts from Felt’s mother, Mitzia, and the MBTA about what happened differed on who was to blame for the accident.

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The elder Felt described a chaotic scene in interviews with news media.

"[My daughter] was struggling and fighting with the door," Felt said told WCVB. "And I was like, 'Oh my god,' and was trying to get the door open with my umbrella. That's when the door popped open.”

Then, she said, she approached the driver before he steered the trolley away from the stop.

"I go in front of the conductor and I'm like, 'Really?'" Felt said. "'Oh I'm sorry. I'm sorry,' [the conductor said]. And then [my daughter] is yelling and screaming, she’s crying."

The next car to approach the stop called in the incident and requested medical attention, according to T records.

The T’s driver offered a different version of the events in an incident report

“After everyone cleared my doors, I was closing my doors and a daughter jumped out of A3 door, and turn [sic] around and put her hand back to the closing door so she could open for her mother,” the operator wrote. “I reacted and I opened the doors back open. I waited for the family and I asked if everything is OK. They mother said, ‘Yes, she is fine, you are all set.’”

Generally, trolley cars rely on T operators’ judgment to control the entryways to train cars, T spokesman Joe Pesaturo said.

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“Motor persons are required to make sure that customers are free and clear of the doors,” he wrote in an email.

MBTA street car doors are also equipped with “sensitive edges,” Pesaturo said, which are “designed to reopen doors if they come in contact with anything.”

He added: “The MBTA strongly discourages people from sticking their arms into a trolley door in an attempt to prevent it from closing.”