Sudden Prey (Lucas Davenport #8) by John Sandford

It begins with a death and ends with one. For months, Lucas Davenport's men have been tracking a vicious woman bank robber named Candy, and when they finally catch up with her, she does not go quietly. In the ensuing shoot-out, she dies – and Davenport's nightmare starts.

For her associates are even worse than she was, particularly her husband, a deeply violent man who swears an appropriate revenge: first he will find the names of those responsible; then he will kill those nearest and dearest to them, just the way they did Candy.