Parents face child abuse charges after toddler kills his nine-year-old brother.

The parents of a two-year-old who accidentally shot and killed his older brother have been arrested, and now face child endangerment and gun possession charges, CBS 5 Arizona reports.

The boys’ 28-year-old mother, Wendy Lavarnia, told police she had left a loaded gun on her bed at her Phoenix, Arizona home on Monday night – within reach of two of her children – while she went to get the holster.

Lavarnia then heard a shot and returned to find her nine-year-old son on the floor and the toddler holding the gun.

Her three other children were also home at the time.

Nine-year-old Landen Lavarnia was taken to hospital in an “extremely critical condition” and placed on life support.

Sgt. Vince Lewis of the Phoenix Police Department confirmed to CBS 5 Arizona later confirmed Landen had died from his injuries.

Landen's father, 31-year-old Kansas Lavernia, was not home at the time of the incident, but reportedly asked officers, "What happened to my kid?" when he arrived at the scene.

He was questioned by police about the gun, which he was not legally allowed to carry or own given he is a convicted felon and a "prohibited possessor".

We just saw this picture on the window at the home where 9-year-old was shot #abc15 pic.twitter.com/KjTgZGhvXo

— Katie Conner (@KatieJConner) March 21, 2017

Kansas was arrested and booked on weapons charges.

Wendy Lavarnia is facing four counts of child abuse "for endangering her children when she placed a gun within their reach, resulting in one child shooting another", Sgt. Vince Lewis confirmed.

It is not clear if her three other children are staying with family or whether they are in the care of the Arizona Department of Child Safety.

A neighbour of the family told CBS 5 Arizona he "felt sorry" about the tragedy.

"It's gun safety," he said.

"You need to keep it locked up and you need to educate your kids that this is not a toy."