Brandon Vilasenor, 28, is charged with first and third-degree murder.
Police responded to the 1300 block of North 13th Street at approximately 9 p.m. for reports of a shooting.
At the scene, investigators found Vilasenor's grandfather with a gunshot wound to his head.
He was pronounced dead at the scene.
Officers have not yet released the victim's identity.
Vilasenor was later taken into custody.