Tunsil was at his mother's house with his mother, Desiree Tunsil, and her husband, Lindsey Miller, Tunsil's stepfather, when the incident occurred Thursday. Tunsil and his mother have since pressed charges against the stepfather, according to Freeze.
"His stepfather shoved his mom and Laremy punched him," a source said. "It's as simple as that. He was defending his mother."
Miller, however, told The Clarion-Ledger (Jackson, Mississippi) that he denies pushing Desiree Tunsil and that Laremy Tunsil was the instigator and hit him six to seven times after an argument.
Miller was granted a restraining order -- which also includes his two sons -- against Tunsil by a Lafayette County judge Friday, The Clarion-Ledger reported.
Tunsil (6-foot-5, 305 pounds) was an All-SEC performer last season and is considered one of the nation's top offensive linemen.
"We can confirm that Laremy Tunsil turned himself in and was arrested for a misdemeanor, domestic violence-simple assault," Freeze said in a statement provided to ESPN. "The incident occurred Thursday night and involves Laremy defending his mother against his stepfather.
"Laremy realizes he could have handled it differently, but I am proud of him for standing up for his mother and protecting his family. Laremy and his mother have also pressed charges against the stepfather. As we gather more facts, we will act and make decisions accordingly."
An Oxford Police Department spokeswoman said Saturday that Tunsil's arrest report would not be available until Monday, when the public information officer is on duty. The spokeswoman also said the police department could not confirm Laremy and his mother had pressed charges against the stepfather until Monday as well.
According to Desiree Tunsil and Lindsey Miller's Facebook pages, the couple was engaged in 2012. They have been married less than a year, a source said.
Laremy Tunsil earned All-SEC honors last season. He suffered a broken leg and dislocated ankle in Ole Miss' loss to TCU in the Peach Bowl on Dec. 31, but is expected to be ready for this season.
Tunsil was projected as the fourth overall pick by ESPN's Todd McShay in his early look at the 2016 NFL draft.
ESPN.com's Chris Low contributed to this report.