A gunman who opened fire minutes after a high school graduation in Richmond, Virginia, targeted an 18-year-old graduate he had a long-running dispute with, police said Wednesday.Shawn Jackson, 18, and his father, Lorenzo Smith, 36, were both killed Tuesday in the gunfire, which sent hundreds fleeing in panic outside the state capital’s Altria Theater after the graduation ceremony for Huguenot High School. Five other people were wounded by gunfire, and at least 12 more suffered other injuries or were treated for anxiety due to the mayhem, according to police.Richmond Interim Police Chief Rick Edwards said the shooting suspect, Amari Pollard, 19, knew Jackson and the two had been embroiled in a dispute for more than a year. Edwards said the nature of the dispute is still being investigated.“This was targeted at one individual. ... That's what we know at this time," Edwards said during a news conference Wednesday.Pollard was arraigned Wednesday morning on two counts of second-degree murder, said Colette McEachin, Richmond’s top prosecutor. Pollard said he intends to hire an attorney, so the court continued the case until a hearing later this month, McEachin wrote in an email. Pollard was ordered held without bond. Court records did not immediately list an attorney who could speak on his behalf.Jackson had just received his diploma at the graduation ceremony and had walked to a nearby park with his father to reunite with the rest of their family when the shooting started, said Tameeka Jackson-Smith, Jackson's mother and Smith's wife. She said Smith was Jackson's father, while Edwards later referred to Smith as his stepfather.Jackson-Smith told The Associated Press that her and Smith’s 9-year-old daughter was hit by a car in the chaos that erupted afterward. The girl was treated for leg injuries and released from the hospital, Jackson-Smith said.Jackson-Smith said the family had watched the graduation, then got separated in a large crowd after they walked outside. “He was so happy — oh my God — because he got to graduate. He worked hard," she said of her son.She said she was walking toward her husband and son when she saw a man run up behind them and start shooting.“He was just running and shooting. I had my daughter beside me and I saw her get hit by a car. My niece almost got hit by a car. I was trying to grab them,” she said.Edwards said police believe Pollard attended the graduation, then went outside, where he had some kind of “interaction” with Jackson, and then then went to his car to retrieve a handgun. Other guns were also retrieved from the scene, Edwards said.Edwards said authorities plan to trace the handgun. He said it was not immediately clear how it had been obtained by Pollard because at age 19, he would not have been able to buy a handgun himself from a licensed dealer.A federal judge in Virginia ruled last month that a federal law banning licensed federal firearms dealers from selling handguns to young adults under 21 violates the Second Amendment and is unconstitutional. The Justice Department has filed a motion asking the judge to put any injunction he may order on hold until the government decides whether to appeal his ruling and until any appeal is decided.No officers were injured in the incident or discharged their weapons, according to Edwards.Richmond Public Schools Superintendent Jason Kamras said he did not personally know Jackson but had shaken his hand and wished him congratulations at the ceremony about 20 minutes before he died.“I can’t shake the image of him receiving CPR on the ground," still in his graduation gown, Kamras said.Jackson-Smith said her son enjoyed rap music and making music videos, and played football, basketball and baseball. “Any sport that he touched he was great at,” she said.She said her husband, who was also called “Renzo,” was an Army veteran and a truck driver.“My husband was so sweet," she said. “He was a caregiver, he was just everything that you could wish for in a person.”The five people wounded by gunfire had injuries not considered life-threatening, Edwards said.The superintendent said all remaining high school graduations will be rescheduled for next week and will be held at schools instead of at the theater. There will be enhanced security, he said.All Richmond Public Schools were to close Thursday and Friday, and school-related events were canceled, the district announced. District employees were still asked to report to work, however, and students and families can go to schools to drop off or pick up items or get meals.Edwards said police are asking people who were near the shooting to call a tip line and send the FBI videos or other images they have on their phones.