Police responded in the area of 11th and O streets at about 10:30 p.m. Thursday.
Authorities said officers were called to the scene by a train operator who heard shots and brought a train to an immediate stop.
Officials tweeted the following message:
RT and SPD investigating a homicide, occurred in the area of 11th and O Streets, on an outbound Lt-rail train.— Sacramento Police (@SacPolice) January 24, 2014
Police said responders found an adult male victim just outside of a train door, fatally injured after being shot multiple times.
Investigators interviewed witnesses and examined video surveillance around the area and inside the train.
A preliminary investigation found that a suspected female shooter fired multiple rounds striking the victim.
Police said the suspected shooter was arrested before making it off the train.
No other injuries were reported.
The investigation is ongoing. Anyone with information can contact police at (916) 264-5471.