The giant retailer shipped billions of opioid pills to pharmacies nationwide. An NPR investigation found employees warned company executives their stores were being used by "pill mill" doctors.

China banned fentanyl last year, but an NPR investigation reveals how Chinese vendors continue to market the chemicals used to make the drug on e-commerce and social media sites.

President Trump promised to end America's opioid crisis. On his watch overdose deaths flattened in 2018 then surged again to record levels.