The video released by the city of Oxford shows the 21-year-old walking out of an Oxford, Miss. bar in what appears to be a white shirt and blue shorts. Kostial is seen hugging someone and leaving the bar at about 11:52 p.m., and is picked up minutes later by a grey van.
Kostial's roommate said the 21-year-old arrived home around midnight. Hours later, deputies found her body about 30 miles from university grounds near a lake in Harmontown. It's unclear what happened between then and when her body was found in Harmontown that morning.
The Lafayette County Sheriff's Department said Wednesday that a preliminary autopsy determined Kostial died of "multiple gunshot wounds" and formally ruled her death a homicide. Classmate Brandon A. Theesfeld, of Texas, has been charged with murder.
Theesfeld was arrested Monday at a gas station in Memphis about 60 miles away from where Kostial's body was discovered, where authorities had tracked his cellphone and credit card, FOX13 Memphis reported. Surveillance photos from the gas station obtained by FOX13 show Theesfeld wearing an Ole Miss t-shirt as he walked into the station.
When he was arrested, Theesfeld had clothes that appeared to have blood on them and a weapon was discovered inside the vehicle, law enforcement officials told FOX13.
The attorney representing Theesfeld is a high-profile and well known in Memphis and the Oxford area, according to FOX2.
Steve Farese, Sr. told FOX2 on Wednesday he has not seen any of the evidence so far, but that he wants to fully interview his client and "see what we can discover on our own." He also shared information about the emotional state of the 22-year-old.
“As you can imagine how you would feel if you were in jail in a state that’s not your home state, overwhelming with the magnitude of what’s going on," he told FOX2.
A former neighbor of Theesfeld, Rex Ravita, told KMOV4 that he was an "arrogant" person when the two lived in the same dorm for a year at the university.
"I'm not going to sugar coat it, he was pretty much a daddy's boy type, constantly had to reference his father's money, how his dad could get him out of anything, just that attitude all the time," Ravita told the television station. "Any type of vulgar comment he could say, any type of rude comment to anybody in our dorm, any of the women."
Ravita added that Kostial and Theesfeld dated on and off for a few years, which he felt was "surprising"
"I truly believe that he manipulated her emotionally to have her believe that he loved her the same way she did, and I think he had her on the hook until the very last second," Ravita told KMOV4.
Ole Miss graduate Aakash Sundar told Fox News' Aishah Hasnie on Wednesday he was in one class with Kostial, though he personally did not know her. He also said that Theesfeld was seen several times at a bar in The Square, an area of the downtown area that has various bars and restaurants.
Sundar described the 22-year-old as "not really a great guy" who "always came off as kind of rude."
"Definitely shocking because he never seemed like, he never looked like the kid that would do something like that," he told Fox News.
Fox News' Talia Kaplan and The Associated Press contributed to this report.