For the first time in decades, the director of the federal Centers for Disease Control and Prevention is speaking out forcefully about gun violence, calling it a "serious public health threat." "Something has to be done about this," CDC Director Dr. Rochelle Walensky tells CNN. "Now is the time -- it's pedal to the metal time." This summer alone has seen a wave of gun injuries and deaths, and the weekends have been especially violent, with an average of 200 people killed and 472 injured by guns each weekend, not including suicides, says the Gun Violence Archive. That's nearly 3.4 people shot every hour every weekend.