A memorial service for 4-year-old Mason Geist, who died Feb. 24 after being struck by a runaway U-Haul truck, is 2 p.m. Sunday in Gardnerville.On Wednesday, father Robert Geist said he would like to set up a trust fund in Mason's name to help hearing-impaired children.“Mason was hearing-impaired. He had qualified for Medicaid, but there were no funds available,” Geist said. “I want to take whatever money people donate and start a trust in his name for kids who need hearing aids.”In greater detail, Geist discussed the accident that claimed the life of his Batman-loving son. “I feel a lot of guilt,” he said. “Everyone is trying to tell me to stay strong for him.”The accident occurred around 3:45 p.m. in the driveway of Chad Lathrop's house, located at 980 Cavelti Road near Spring Valley.Geist said he'd picked up the U-Haul truck in Gardnerville to help his cousin move that day. He said he drove the U-Haul to the residence by himself, while Tina Lathrop, Chad's wife, drove Geist's normal truck with Mason in a car seat. As Robert attempted to park the U-Haul in the driveway, which is situated on an incline, Mason and other relatives were outside waiting, Geist said. “I just thought it was the safest place for him, to get him in the U-Haul with me,” Geist said. “I got out to see if we could back up more. The truck started rolling. It happened so fast.”Geist said Mason was not restrained in the cab of the vehicle. He said he was sure he placed the vehicle in park before stepping out and leaving the door open. He said he checked clearance on the passenger side, while his nephew, Lathrop's teenage son, checked the driver's side. Then the truck began rolling downhill. Geist thought he'd applied the emergency brake, a hand-lever mounted beside the driver's seat, before getting out. He said he definitely remembers putting the vehicle in park. When the truck took off down the hill, family members chased it, attempting to reach Mason. But the boy fell out and was struck by the vehicle. He was later pronounced dead at Carson Valley Medical Center.U-Haul corporate is cooperating with the Douglas County Sheriff's Office's ongoing investigation into the incident. Anyone wishing to assist the family can make donations to the Mason Allen Geist account at any El Dorado Savings Bank branch. The account No. is 5000423.The service is at Walton's Funerals & Cremations, 1521 Church St.