Far Gone by Laura Griffin.
Detective Andrea Finch was in the wrong place at the wrong time. When a teenage assailant pulls a gun in a restaurant and threatens his girlfriend and possibly anyone else he can, Finch shoots him. She is now on leave and her job in jeopardy.
If things aren't bad enough she is afraid her younger brother is in some serious trouble. At least she has plenty of time to investigate this situation.
There is a romantic interest that develops between Finch and an undercover FBI agent who is interested in what her brother is up to, as well. I didn't find either the romance or the plot terribly interesting.
NetGalley/ Gallery Books
Crime. April 15, 2014. Print version: 384 pages.