Ignoring lessons of past civil disturbances such as the Rodney King riots in Los Angeles, police inflamed tensions that have fueled more than a week of unrest in a St. Louis suburb where an officer shot to death an unarmed black teenager.

The challenges are as basic as the overwhelmingly white composition of the police department in predominately black Ferguson, Missouri, and a decision to quickly embrace aggressive tactics, current and former police officials said.

While officials interviewed agreed that local authorities were acting in a manner they thought best in a difficult situation, inexperience, a chasm in the relationship between officers and the community, and a disregard of lessons learned by larger police agencies have made it harder to quell the strife, they said.