Stuffed animals decorate the chain-link fence as a memorial to Tremain, shown on the poster in his football uniform.
"You're in the Big 12 now," one child wrote, referring to the college football conference.
"We'll miss you," says another.
Residents in this working-class community of 15,000 are grappling with Tremain's shooting death — especially the possibility that a 10-year-old playmate may have been responsible.
"This is the first time I've dealt with anything in my career this young of age as a homicide," police chief Fred Savage said.
The friend, who lived a few blocks away, was arrested and jailed on a murder complaint.
"They were practically raised together," said Tremain's mother, Tiffany Gillispie. "They always played well, they never got in fights. They always spent the night together."
Police said they don't think Monday's shooting was an accident, but they have not established a motive.
CBS News Correspondent Bob McNamara reports Tremain Richey's talent and popularity, and perhaps a friend's jealousy, may have had a role the killing, according to neighbors.
Gillispie said that when she got home from work Monday, her son, who was supposed to be looking after his 5-year-old sister, was not there. The girl told her mother she didn't know where Tremain was, and the two went driving around to look for him.
It was then that the girl told her mother Tremain had been shot.
They returned home and Gillispie found her son lying dead in the yard near the back of the house.
It is unclear if the 5-year-old witnessed the shooting, though she was home at the time. Police said there was a juvenile witness, but didn't say whether it was the victim's sister.
"He loved football, he wanted to go to the pros," sobbed his mother. "He said it all the time: 'Mom, I'm gonna make you rich, I'm gonna...'"
Sandwiched between two bustling highways, this town 30 miles west of Oklahoma City is known for its truck stops. Youth violence is hardly commonplace here, and Tremain's death has left the town in shock.
"This boy knew right from wrong," said Anna Palmer, Tremain's great-grandmother. "He knew not to come down here and point a gun at his friend's head. We just want to know why."
Neighborhood children reported seeing the suspect carrying a weapon.
Police said they found the gun believed to have used in the shooting at a home nearby. It was wrapped in a blanket inside a garage, Savage said.
The suspect was in police custody at a juvenile detention center, and a closed hearing was held Thursday to determine if there is enough evidence to keep him in custody. Attorneys refused to discuss the hearing, citing a gag order imposed by the judge.
The boy has not been charged and his name has not been released.
Tremain's family describes the shooting victim as a quiet child who excelled at sports and school.
"He led by example," said Estavion Trotter, Tremain's uncle. "He didn't say much until he got to know you, but he was a pretty good kid overall."
The police chief, like so many other El Reno residents, was struggling to understand what had happened in his quiet town.
"We have problems just like any other city," Savage said. "But we've never had anything like this. A 10-year-old shooting a 10-year-old is just not normal."