In 2019, Brandon McDowell was contacted by a sophomore in college who asked to buy Percocet, a prescription painkiller. What the 20-year-old sold her instead were counterfeit pills laced with fentanyl, a deadly synthetic opioid that can be lethal in a dose as small as 2 milligrams. Hours later, Alexandra Capelouto, also 20, was dead in her Temecula, California, home. It is an increasingly common scenario as fentanyl overdoses have become a leading cause of death for minors in the last five years, with more than 74,000 people dying in the U.S. from a synthetic opioid in 2023, according to...