Denver’s decision to welcome migrants with open arms is bringing bloodshed to the suburbs next door. A notorious Venezuelan prison gang has set up shop in Aurora, Colorado — even though the town wanted no part of the influx of asylum seekers in the first place. Aurora — a quiet bedroom community with a population of 390,000 directly east of the Mile-High City — has become a base of operations for the brutal Tren de Aragua gang, which has seized multiple apartment complexes and set off a wave of violent crime. Denver leads the nation in new migrant arrivals per-capita,...