The bodies were found around 5:30 p.m. Monday at a house in the town of Angier.
Officials with the Johnston County Sheriff's Office said the boy and girl were both just 14 years old. Their identities are not being released because of age.
While the boy was identified as a local high school student, a neighbor said the girl was homeschooled.
Deputies said the boy's father was the one who found the bodies.
"He started crying, he was screaming in the front yard," neighbor Cheyanne DeRossa told ABC11.
Police did not say who died as a result of murder and who committed suicide.
Johnston County major crimes detectives have secured Angier crime scene, now awaiting search warrant to re-enter home to investigate how the two people died. pic.twitter.com/LrSvQU7UcW— Joel Brown (@JoelBrownABC11) September 25, 2018
In the minutes after the bodies were found, neighbors said they heard screams of desperation from a man and woman who made the grisly discovery.
"When they came out, we heard a lot of screaming, 'Oh my God, no. Oh my God, no,' next thing we know, there's cops and a crime scene," said Stephane Wirth, who lives next door with her three daughters.
About 9 p.m., deputies obtained a search warrant to enter the home.
The coroner arrived at the scene around 10 p.m. to remove the bodies.
All of the neighbors said the family mostly kept to themselves.
"They were a really nice family," DeRossa said. "They were outside a lot. BBQ a lot. It's all really shocking. They seemed really happy."