A pastor's teenage son has accidentally shot and killed his younger cousin while they were searching for intruders at the church attached to his home.

The tragedy occurred at the Christian Faith Center church, Willmington, Illinois. The 17-year-old and his 15-year-old cousin were together in the church house when they thought they heard an intruder, according to the Chicago Tribune.

The older boy, who has a valid firearms certificate and has been trained in gun use, took a rifle from his parents' bedroom and tripped over an extension cord while they were checking the premises. The gun went off and he shot his cousin in the chest.

Police described the event as a 'tragic accident'.

The boy – named by a family member as Mikey Wilkey – was pronounced dead after being taken to hospital.

Police said no charges were being brought.

Mikey's half-sister Danielle Picciola said the boys had been close ever since they were children.

'They were really close. They hung out all the time,' she told the Tribune.

She said their faith was helping them cope. 'We're not very religious, but we do believe in God and we know that he's in a better place. He's with our grandpa and he should be happy with him up there.'