The lawyer for the Massachusetts transit operator at the center of a runaway train incident says his client was forced to miss a disciplinary hearing because of stress-related illness.

The lawyer, Phillip Gordon, said David Vazquez feels terrible about what happened but cautioned against jumping to any conclusions about his client's actions.

Gordon says Vazquez was under doctor's orders to call in sick for Monday's scheduled hearing.

The driverless train left a suburban Boston station on Thursday morning and rumbled through several stops before transit workers stopped it by cutting power to the rails. No passengers were hurt.

Gov. Charlie Baker has said the operator appeared to violate several safety procedures.

Gordon says his 53-year-old client has a long record of safely driving trains and is cooperating with the probe.