In the early morning hours of a Thursday in Arivaca, Arizona, deputies responded to a call around 1 a.m. and found 33-year-old Kaycie Mattias fatally wounded inside a residence. Her 55-year-old mother, Monica Gilkey, was also found with gunshot wounds, was taken to a local hospital, and later died of her injuries.

Witnesses said the shooter fled the scene. Their accounts led deputies to identify 36-year-old Justin Tyler Grandstaff. An alert and assistance from the U.S. Border Patrol resulted in Grandstaff’s apprehension at the Arivaca Checkpoint; he was booked into the Pima County jail and faced two counts of first-degree murder. At the time of the arrest the motive for the shootings had not been made clear.

The small community of Arivaca was left reeling by the killing of a mother and daughter in one incident. If anyone knew Kaycie Mattias or has information about what happened that night, please come forward.