Already this year, enough fentanyl has been seized at the U.S.-Mexico border to kill every American citizen -- twiceMore Americans than ever before are dying because of fentanyl, and agents with Customs and Border Protection's Office of Field Operations say the Mexican cartel could be partly to blame. Already this year, enough fentanyl has been seized at the U.S.–Mexico border to kill more than 700 million people. One kilogram, just over two pounds, of fentanyl has the potential to kill 500,000 people, according to the Drug Enforcement Administration.