WASHINGTON, Oct. 1 — Guards working in Iraq for Blackwater USA have shot innocent Iraqi civilians and have sought to cover up the incidents, sometimes with the help of the State Department, a report to a Congressional committee said today.

The report, based largely on internal Blackwater e-mail messages and State Department documents, depicts the security contractor as being staffed with reckless, shoot-first guards who were not always sober and did not always stop to see who or what was hit by their bullets.

In one incident, the State Department and Blackwater agreed to pay $15,000 to the family of a man killed by “a drunken Blackwater contractor,” the report said. As a State Department official wrote, “We would like to help them resolve this so we can continue with our protective mission.”

The report was compiled by the Democratic majority staff of the House Committee on Oversight and Government Reform, which is scheduled to hold a hearing on Blackwater activities on Tuesday. That hearing is sure to be contentious now that the chairman, Representative Henry A. Waxman, Democrat of California, and other members have the staff’s findings to study.