An everyday family dinner in the Belgian city of Antwerp came to a sudden halt earlier this year when gunfire boomed outside. Four family members around the table were shot, including an 11-year-old girl who died from her injuries. The deadly shooting in the quiet suburb lined with squat brick buildings shed light on the dark side of the port city’s most lucrative trade: cocaine trafficking. The victim was the niece of two of Belgium’s most notorious fugitives, wanted internationally for drug trafficking and money laundering: Othman and Younes El Ballouti. The younger, Younes, manages his older brother’s cocaine business....