This is not how Gen. McChrystal wanted the Marja operation to start. From an ISAF press statement:

Two rockets from a High Mobility Artillery Rocket System (HIMARS) launched at insurgents firing upon Afghan and ISAF forces impacted approximately 300 meters off their intended target, killing 12 civilians in Nad Ali district, Helmand province today.

ISAF Commander Gen. Stanley McChrystal conveyed his apologies to
President Hamid Karzai for this unfortunate incident.

“We deeply regret this tragic loss of life,” said McChrystal. “The current operation in Central Helmand is aimed at restoring security and stability to this vital area of Afghanistan. It’s regrettable that in the course of our joint efforts, innocent lives were lost. We extend our heartfelt sympathies and will ensure we do all we can to avoid future incidents.”

According to the release, McChrystal suspended the use of HIMARS. This is awful. For a mission predicated on protecting the population, it’s doubly so. At least McChrystal and ISAF didn’t follow in the footsteps of some of their predecessors and stall/make excuses/deny responsibility for the error. This is in the spirit of Defense Secretary Gates’ (much neglected) “first apologize” rule from January 2009 about what to do in the event of Afghan civilian casualties.