A murder-suicide in Ionia County is still under investigation, as deputies are unsure of a motive at this time.

On January 6, just before 9:40 p.m., an Ionia County deputy was sent to help a driver on I-96 near Nash Highway in Boston Township.

When he arrived on the scene, the deputy discovered a silver Chevrolet Equinox parked on the side of the road with the lift gate and passenger doors open, according to a press release from the Ionia County Sheriff's Office.

There were also two deceased victims on the shoulder side of the road -- a third victim was inside the SUV, injured from an apparent gunshot wound.

The deputy aided the victim inside the vehicle until other officers and emergency responders arrived. David and Lisa Somers, both 50 years-old from Kaleva, Mich. were pronounced dead at the scene. A loaded shotgun was found directly under David Somers' body, the press release states.

At this point, all indications are that David Somers was the gunman and both David and Lisa died from gunshots to the head, said Ionia County Sheriff Dale Miller.

The Ionia County Sheriff's Office said it is looking at a lead that David Somers may have been treated for a recent brain ailment.

The third victim was 18-year-old Amedy Dewey, Lisa Somer's daughter. Dewey was taken to a Grand Rapids hospital for treatment. She is in critical, but stable condition, according to authorities.

Amedy and Lisa were returning home from vacation and were picked up by David at the Gerald R. Ford International Airport. They were headed to the Midland area.

The family was very close, said Ashley Vos, Lisa's longtime friend and softball teammate.

"[Lisa] was always funny, always positive about everything" Vos said. "She almost always had a smile on her face. I never thought something like this would've ever happened."

On the night of the incident, David and Lisa's residences were checked by Manistee County Sheriff deputies to make sure there were no other victims. No one was found.

The Ionia County Sheriff's Office said there is no clear motive at this time to what lead to the homicide. The incident remains under investigation.

Vehicle at the scene of murder-suicide in Boston Township, Mich. on Jan. 6, 2018

Correction: A previous version of the story said that one of the victim's was named Amber Dewey.

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April Stevens is a multi-platform producer at WZZM 13. Have a news tip? Email news@wzzm13.com, visit our Facebook page or Twitter.