(ABC News)

A 5-year-old boy is dead after a shooting inside an apartment Friday morning in Lakewood, Colo., and police say a 3-year-old boy pulled the trigger.

Police said they believe the shooting was accidental, but one of the adults in the apartment at the time, Adam Laham, 23, was arrested on charges of child abuse resulting in death and criminal negligence.

Laham appeared in court this morning and his bond was set at $40,000, according to KUSA-TV in Denver.

Lakewood Police Department spokeswoman Bonnie Martin said Laham was at the residence along with several other adults, when the shooting occurred.

Laham, who was not related to either of the children and was visiting from Kansas, owned the gun that the 3-year-old fired, police said. Police declined to say how the shooting occurred or what kind of gun was used.

The 5-year-old boy was taken to the hospital with a gunshot to the chest and later died, Martin said.

Photos of guns were found by ABC News affiliate KMGH-TV in Denver on the Facebook page of a family member listed as a resident of the apartment where the shooting happened. Hours later, the same man posted "One *blank* second changes everything, forever."

Neighbors say the family that lives in the apartment is friendly, and were just seen having a snowball fight in the yard on Thursday.

"It's very sad. I wasn't expecting anything like this," said Joyce Loffer, who lives next door to the unit where the shooting took place.

The relationship between the children has not been released, but both lived at the residence where the shooting occurred.

ABC News affiliate The Denver Channel contributed to this report.