Amedy Dewey, the 18-year-old girl who survived being shot the head as part of the murder-suicide that occurred along I-96 in Ionia County, has provided investigators with more details about what happened the evening that her stepfather, David Somers, allegedly shot and killed her mother, Lisa Somers, before turning the gun on himself.

A release from the Ionia County Sheriff's Department details some of the things they've been able to determine from speaking to Amedy.

What were they doing in Ionia County? Dewey and her mother, Lisa Somers, had just returned to Michigan from a cruise on January 6, 2018 by flying from Florida into the Gerald R. Ford International Airport in Grand Rapids. David was also supposed to go on the cruise, but decided the day before they were set to leave that he wasn't going to join his wife and stepdaughter. David picked up Lisa and Amedy at the airport, and drove for somewhere between 20 and 30 minutes before the shooting occurred.

Lisa and David were arguing. Dewey told investigators that her mother and stepfather were arguing in the car. According to Dewey, Lisa accused David of infidelity earlier in the day via phone and text message and the argument continued after he picked them up from the airport.

David was driving erratically prior to the shooting. As the argument continued and David became more angry, he began driving erratically - he was reportedly travelling at excessive speeds. The driving was reported by several witnesses who contacted the Ionia County Sheriff's Department in the days following the shooting.

"He's got a gun!" Dewey told investigators that David Somers eventually slowed down and pulled off to the shoulder of the road in Ionia County. He then exited the vehicle and walked to the back of the car. Dewey and her mother both exited the vehicle, and that's when Dewey says her mother yelled, "he's got a gun!"

Dewey attempted to hide from David Somers. After her mother's warning, Amedy got back into the vehicle's back seat and attempted to lay across the seat and hide. She told police that she attempted to call 9-1-1 before Somers shot her. Amedy did not see or hear what happened to her mother.

“I’m not going to die. This is not how I’m going to die!” Amedy told police that her immediate thought was, “I’m not going to die. This is not how I’m going to die!” She did several things in an attempt to save her own life, including trying to use her cell phone to call for help, climbing over the front seat to use the horn and lights on the car, and even getting out at one point to try and flag down passing motorists. Witnesses who called police that evening reported seeing someone at the back of the car looking like they were trying to flag down cars.

Lisa Somers was shot second. Investigators determined that after David shot Amedy, he turned the gun on his wife and shot her once. He then turned the gun on himself. It is unknown if David Somers was under the effect of alcohol or narcotics, pending toxicology reports.

Family claims David was being treated for a brain tumor or mass. Members of David Somers' family told police that he was being treated for a brain mass or brain tumor. Police have not determined if this factored into the shooting, and it's unlikely that they will ever find out for sure.

Police say Dewey exhibited courage, tenacity, and strength. The release from the Ionia County Sheriff's Department ended by commending Amedy Dewey for the "courage, tenacity, and strength" she has displayed during and after the ordeal as she continues here recovery.

More From 98.7 WFGR