A 12-year-old boy stabbed his 13-year-old brother during a fight over what to watch on television, police said.

The 13-year-old was listed in extremely critical condition Monday night. The brothers were fighting in the living room of their southwest Phoenix home Monday afternoon.

The younger brother allegedly went to the kitchen, returned with a knife and allegedly stabbed his brother once in the abdomen with a 5-inch blade, said Phoenix Police Lt. Rob Howe.

The boys' father heard them fighting over the TV. He entered the living room and the victim told his father he had been stabbed by his younger brother before collapsing, Phoenix Police Sgt. Joel Tranter said.

A 7-year-old sister was home but in a different room at the time of the stabbing, Howe said. Police are treating the house as a crime scene and are still investigating.

The suspect was in custody Monday night, Tranter said.