On a September afternoon, Allyssia Solorio wondered why her energetic young brother hadn’t emerged from his bedroom in their Sacramento, Calif., home. When she opened his door, she saw 23-year-old Mikael leaning back on his bed with his legs dangling over the side. She rushed to her brother and shook him, but to no avail. He was dead. A counterfeit pharmaceutical pill laced with illicit fentanyl had killed him.