"When you're consciously deciding that you're going to try to hit a certain point of 100 mph, on a rainy road ... you don't care," said Mosley. "For any other young person out there that's thinking about doing this, they can see that we're serious about pursuing charges when you hurt somebody to this extent."
Wentworth Maynard was driving the car McGee rear-ended. Maynard had just turned right out of his apartment complex onto Tara Boulevard, where the speed limit is 55 mph.
Maynard spent several weeks in a coma and now has a traumatic brain injury. His family is suing the teen and Snapchat for encouraging reckless behavior.
In newly filed court records, McGee admitted going 90 mph but denied using the Snapchat app at the time of the crash.
The speed filter allows the user to capture the speed at which they're moving at the time the picture or video is recorded, and posts the speed over the picture.
Snapchat released a statement saying, "No snap is more important than someone's safety," adding that the app discourages use of the speed filter while driving by including a warning message when someone first uses it.
"A vehicle is a weapon, and the faster you go, the more likely it is that you're going to hurt yourself or somebody else out there," said Mosley.
Mosley sent her crash reconstruction expert to help Lovejoy police assess the case after a Channel 2 investigation last month revealed the police department had initially failed to determine McGee's speed during the crash and, instead, attributed the cause to Maynard.
"He could have asked some more questions," Lovejoy police Chief Mark Harris said of the officer who initially responded to the crash.
Harris acknowledged he didn't become aware of the Snapchat allegations until WSB asked him about the crash following an April 5 open records request.
"Had we known about this earlier, we would have probably come to this conclusion earlier in the investigation," Harris said.
He directed his patrol officer to re-interview McGee's three passengers, all of whom admit the teen was pushing 100 mph and using Snapchat, including her ex-boyfriend, Henry Williams, who initially defended McGee.
"He's recanted his story and stated that she was running closer to 100 mph," said Harris.
McGee's former co-worker, Heather McCarty, who was also a passenger in the car, has maintained from the beginning that McGee was driving more than 100 mph. That was written in her original statement she gave at the hospital, but the investigating officer initially overlooked it.
Harris applauded McCarty for speaking out about what she witnessed, saying none of this would have come to light otherwise.
He hopes the charges send a clear message to McGee and other young drivers.
"The main thing I would like to see out of it is that she understands that what she was doing was wrong, and based on her doing wrong, what kind of injuries she caused to an innocent person," Harris said.
McGee's attorney did not return a call for comment.
"On behalf of the Maynard family, we are thankful for the Lovejoy Police Department's diligence in investigating this crash and their efforts to keep us safe from distracted driving," said Michael Neff, the Maynard's family attorney. "We look forward to pursuing justice against Snapchat and Ms. McGee."
EXCLUSIVE: Jodie Fleischer, WSB-TV has learned the teen admits going 90 mph, but denies using the app.Posted by WSB-TV on Wednesday, June 1, 2016