An unidentified woman tries to reopen the commuter train door before it takes off with the little boy's father still inside.

PORTLAND, Ore. - A 3-year-old boy was left stranded at a commuter train platform when a door on the train malfunctioned, separating the toddler from his dad.

Surveillance camera footage of the incident was released Friday. The incident took place Monday at the S.E. Main Street Station in Portland, Ore.

According to TriMet, which operates the train, the boy pushed the accessible ramp button on the door as he was getting off the train, causing it to open and then close again to deploy the ramp.

TriMet officials say the door should have reopened but it didn't and the father and son were separated. They are investigating, saying the ramp deployment process may have been overridden, causing it to be interrupted. It is unclear what the driver was doing at the time.

A woman who was standing on the platform tried to get the door to open, but couldn't and the train took off. She ended up staying with the boy until his father returned seven minutes later from a returning train.

The father reported that he tried to push the intercom button inside the train to contact the operator but got no response. TriMet officials say it appears there was a malfunction with the intercom.

TriMet says they do have clear protocols for dealing with this type of a situation and once an operator was made aware of what happened, those protocols were followed. TriMet says they have been in contact with the father and did apologize to him. They also gave him two free annual passes.