Decades after the unidentified bodies of a woman and a 10-year-old boy were found in separate states beside a Southern interstate highway, investigators now say they were a mother and son and the boy’s father has confessed to killing them.

The case was cracked thanks to an online DNA database, help from international police and a consultant whose work led to an arrest in the Golden State Killer investigation, authorities in North Carolina and South Carolina said Tuesday.

But investigators in both states said they had never stopped trying to solve the 1998 cases that they never knew were related, separated by 215 miles along Interstate 85.

“I always kept the case file box under my desk, where it was purposefully in my way. Every time I turned, I hit it with my leg. I did this so the little boy couldn’t be forgotten,” said Orange County, North Carolina, Sheriff’s Maj. Tim Horne, who worked the case from the beginning.