mass killings in Iraq

Seems like at least twice a week we hear about numbers of dead bodies being dumped around Baghdad. They are all men, and show signs of torture. Many have been decapitated.

What the news outlets never mention is who these people are? Are they all Shiite or Sunni? Are they just the victims of kidnapping for ransoms that are never paid? Are they politically motivated? Are they suspected terrorists or insurgents? See where Im going with this?

Is it possible they are insurgents or terrorists and are bieng killed by Iraqi forces or US covert OPS?

If anyone has more info or ideas about this I'd like to hear>

Thanks

Thought I'd try this one more time to see if anyone:

1) is interested
2) has any ideas
3) has actual knowledge regading the topic

Thanks