PLAISTOW, N.H. – On an autumn afternoon in 2014, Jim Zanfagna received a phone call from his son-in-law, alerting him to a string of alarming messages that were surfacing on Facebook. His 25-year-old daughter, Jacqueline, had died, and friends were posting condolence messages before the Zanfagnas ever heard from authorities.“Social media learned before we did,” Zanfagna said, as he fought back tears inside his Plaistow, N.H., home. The cause of death was an accidental overdose from heroin laced with fentanyl, a powerful synthetic opioid that is killing more people in New Hampshire than in any other state. Fentanyl is deadly at two milligrams – akin to a few grains of salt – making the risk of a fatal overdose high. While the drug is commonly used by hospitals, it is also made illicitly in China and imported into the U.S. by Mexican drug cartels.