Police calls for nonfatal overdoses are down 50 percent this year, said Scott Thomson, chief of the Camden County Police Department, which covers the city. But fatal cases — people who couldn't be revived or died on the way to the hospital or in the emergency room — are up more than 50 percent. The reason appears to be fentanyl, Thomson said, which is so potent that the reflex to stop breathing can kill the user before police can even be summoned. Most of Camden County's deaths occur in the city, especially around the Walter Rand Transportation Center and nearby streets, although a majority of those who died resided elsewhere and may have been in the city solely for drugs.