Vertical coffin

In SWAT circles, a doorway is known as a "vertical coffin," since anyone stepping through one is at their most exposed. The story opens with that danger made real: a Los Angeles sheriff's deputy is shot dead on a front porch while carrying out an ordinary warrant. The Bureau of Alcohol, Tobacco and Firearms had passed the arrest to the Sheriff's Department, but left out a key detail: the suspect was believed to be hoarding a large cache of illegal weapons.