(AP) – A spate of mass shootings and violence across the U.S. over the weekend killed at least six people including a Pennsylvania state trooper and left dozens injured. The shootings follow a surge in homicides and other violence over the past several years that experts say accelerated during the coronavirus pandemic. They happened in suburban Chicago, Washington state, central Pennsylvania, St. Louis, Southern California and Baltimore. Experts disagree over causes of the increased violence. It could be due to the prevalence of guns in America, less aggressive police tactics or a decline in prosecutions for misdemeanor weapon offenses.