More details have been released surrounding the shooting deaths of a father and daughter in Woodward. Police say the suspect, 30-year-old Shane Cole Allison, knew the victims and admitted to planning the attack.

The victims have been identified as 81-year-old Gary Mulbery and his 42-year-old daughter, Christina Alewine. According to investigators, the three had arrived at Walmart together along with Allison’s mother. While Mulbery and Alewine were loading groceries into their vehicle, Allison reportedly exited the car and opened fire, killing both before fleeing the scene.

Police apprehended Allison nearby the Woodward High School, where he was found carrying a .22 caliber revolver and a bag containing additional weapons and ammunition. Authorities say Allison confessed to the shootings and admitted he had planned the attack the day before.

Investigators later searched Mulbery’s property, where Allison had been living, and recovered parts of the firearms Allison allegedly modified to carry out the attack. Prosecutors have since charged Allison with two counts of first-degree murder and two counts of possessing sawed-off firearms.

Authorities are investigating whether a dispute over living arrangements may have played a role in the shootings, as Mulbery reportedly owned the property where Allison and his mother resided.