Boy (3) shoots 18-month-old brother dead
A three-year-old boy shot his 18-month-old brother dead after the youngsters found a handgun in a neighbour's apartment, police in central Arizona said.
Payson Police Chief Don Engler said his department's investigation into the shooting will take about a week and the results will be forwarded to the Gila County Attorney's Office for a decision on whether to prosecute anybody.
Mr Engler said the probe is focusing on the securing of the gun, which he said was not in plain sight in the living area of the neighbour's apartment.
The boys and their mother were visiting the neighbour when the siblings found the semi-automatic handgun and took it to another room.
Mr Engler said neither adult knew the boys had the weapon.
Payson is about 90 miles (145km) north-east of Phoenix.