Greg Ramos

Greg Ramos, currently 15 and born in Florida strangled his mom to death over a bad grade.

Greg Ramos wore a blank expression when he was appeared in court.

Police say Ramos and his mother argued Thursday after he came home with a D grade. Around midnight, he sneaked into his mom's bedroom and choked her, police said. Then he went to get a wheelbarrow to carry the body out of the house and when he returned he discovered she was still alive, authorities said. He told police he choked her for 30 minutes until she was dead.

Ramos called two school friends, who allegedly helped him bury his mother, Gail Cleavenger, 46, in a fire pit outside Orlando.

“This is where he and his friends would come,” County Sheriff Mike Chitwood said. “Unfortunately her foot was protruding after digging down eight or 10 inches. It's not really a big place to bury his mom.”

Chitwood called Ramos "soulless."

Initially, the teen told police he came home from school and found his house had been ransacked and his mother was missing. During questioning, he calmly acknowledged  killing his mother, police said.

“Normally, you figure there is a point in time when someone is going to breakdown, but there was no emotion. There was nothing at all like that,” Chitwood said.

Criminologist Dr. Casey Jordan spoke to Inside Edition about the killing.

"These kids, very often we don't see the signs because they are showing no emotions at all -- they are what we call 'flatline,'" she said. "They show no sympathy, no apathy, no remorse."

Video obtained by Inside Edition showed Ramos performing taekwondo at a martial arts camp in 2015. His mom was there and cheered him on.

Ramos was a member of The Police Explorers Youth Group. He wanted to be a homicide detective. His favorite course was criminology.

Friends say his mother was a loving woman whose last post on Facebook was a photo of her son when he was 6. “Love this face,’ she wrote.

Dawn Marie, a family friend, told Inside Edition Ramos is "not the monster they say he is," adding, "he was brought up in a loving home by loving parents."

Ramos' father was away on business at the time of the killing.