Fineberg said he expected to raise at least $10,000, which would've covered the cost of Mitchell's funeral.
Mitchell, 17, was on his way to Westfield for a football scrimmage last Friday afternoon when a fight broke out between Mitchell and 19-year-old Emile "Rusty” Lewis over ownership of a dog, according to police.
Police said Lewis went to his apartment and returned with a rifle, shooting Mitchell several times and killing him.
Police have arrested Lewis and charged him with murder.
Coming into this season, Mitchell was regarded as one of the top high school football players in Texas.
The 6-foot, 200-pound outside linebacker had several college scholarship offers but chose the Sooners in June.
"I told OU I'd be happy to give them the e-mails and names of everyone that contributed to me,” Fineberg said.
"The point was to help Mitchell's family.
"I don't care who it comes from.”