A woman has been stabbed to death on a Chicago L train in what police say may have been a domestic dispute.

First Deputy Superintendent John Escalante said Thursday that witnesses said they were a couple and there was "some talk about a child." Escalante said witnesses observed the man asking the woman a question. After she said "no," he stabbed her and slit her throat.

The attack was recorded by surveillance cameras.

Escalante said several people called 911. A police officer who was near the station the train was entering went to the platform and arrested the man.

The attack happened on the Chicago Transit Authority's busiest L line, the Red Line. It shut down one station for nearly two hours.