Oakland County Child Killer docuseries chapter 4: The investigation

Someone killed at least four children in Oakland County, Mich. between 1976 and 1977.

Investigators have been working for decades to determine who the serial killer is and if he is still alive. Those who knew the victims -- their families, friends, classmates, teachers, coaches and neighbors -- have been forever changed by what happened during the 13-month period from February 1976 to March 1977.

In that time, the four children were abducted and murdered with their bodies left in various locations within or just outside Oakland County.

After the murder of Timothy King in 1977, police assembled the lagrest task force in U.S. history at the time. It includes officers and detectives from police departments across the area.

Police knew they had a serial child killer on their hands.

Watch Child Killer Chapter Four: The Investigation in the video player above.

Here are the five parts to the docuseries:

• Chapter 1: North Fox Island
• Chapter 2: Out in the cold
• Chapter 3: Timmy King
• Chapter 4: The investigation
• Chapter 5: Suspicion