Omaha Police have made a second arrest in the Walmart Shooting that killed 21-year-old Kayviaun Nelson .
On Tuesday afternoon, OPD confirmed Marcus Wheeler, 19, was in custody.
Five days ago, 17-year-old Daion Williams was arrested on suspicion of first-degree murder. According to prosecutors, before the fatal shooting, Nelson, Williams, and Wheeler got into a fight at a Dollar General store . Nelson reportedly drove away; Williams and Wheeler followed her to Walmart.