Graham Dillon, 37, appeared in court on Tuesday morning charged with murdering his son, Bradyn Dillon.

Mr Dillon, wearing shorts and a grey T-shirt, appeared stunned as he entered the courtroom. He did not sit with his Legal Aid duty solicitor at the bar table. He entered no plea to any charge, and made no application for bail. He was remanded in custody at the Alexander Maconochie Centre until March 1.

The street in Jacka, on the northern fringe of Gungahlin, remained closed on Tuesday as detectives took witness statements from neighbours and forensic teams investigated the scene.

One neighbour, Tammy Kirchner, sobbed as she remembered seeing a paramedic gently carry the boy from the home on Monday evening.

The boy was rushed to Canberra Hospital where he later died of his injuries.

Moments after paramedics retrieved the boy, a man appeared with his hands up.

"He was put into handcuffs, he was thrown on the ground," Ms Kirchner said.

The boy often played with the scores of kids who spilled out onto the neighbourhood of an evening.

The family had moved into the sleepy pocket only 12 months earlier.

From the outside, the house appeared unlived-in, with overgrown grass reaching waist height and catalogues overstuffed in the mailbox.

On Tuesday morning, the porch light was still on but the curtains were drawn.

A father who lives nearby said he would be holding his children extra close tonight.

Another said, "I have three daughters under eight and I took the day off work to walk them to school."

Ms Kirchner said she didn't want to stay in the suburb, which was usually quiet and filled with families.

"I can't look up there," she said.

Police ask anyone who may have witnessed the incident, or has any information that could assist the investigation and has not yet spoken to them, to contact Crime Stoppers on 1800 333 000, or at act.crimestoppers.com.au.