According to an AP article and a Defense Department report:
Private security contractor Blackwater USA has had to fire 122 people over the past three years for problems ranging from misusing weapons, alcohol and drug violations, inappropriate conduct and violent behavior…
…Blackwater has been involved in 195 shooting incidents since 2005, or roughly 1.4 per week.
In more than 80 percent of the incidents, called “escalation of force,” Blackwater’s guards fired the first shots even though the company’s contract with the State Department calls for it to use defensive force only
Previous post on Blackwater, national “defense” and accountability (or the lack thereof), here.