WEST COLUMBIA, S.C. (AP) — Lexington County deputies say a Baltimore man shot and killed his live-in girlfriend as they drove to pick up their son who was staying with relatives in South Carolina.

Investigators said 22-year-old Genesis Pearson was not far from the West Columbia home where his 13-month-old son was staying when he shot 21-year-old Alishia Dorsey in the head around 1:45 a.m. Sunday.

Deputies say they haven’t figured out why Pearson killed his live-in girlfriend.

Pearson was arrested at the scene of the shooting and has been charged with murder. He is being held in the Lexington County jail without bond, and it wasn’t clear if he had an attorney.

(Copyright 2012 by The Associated Press. All Rights Reserved.)