Mechanical Error

"A US soldier in Afghanistan has killed at least 16 civilians and wounded five after entering their homes in Kandahar province, senior local officials say.  He left his military base in the early hours of the morning and opened fire in at least two homes; women and children were among the dead.  Nato said it was investigating the "deeply regrettable incident"."  NATO will inevitably find that the shooting was due to a "mechanical error."