Texas Killing Fields

Rhino (Stephen Graham) is behind the series of murders (whether he's been preying on women since 1971 is unclear), while his accomplice is none other than Eugene Sliger (James Landry Hébert), older brother of Little Anne Sliger (Chloë Grace Moretz) who is kidnapped for talking to the cops.

Brian Heigh (Jeffrey Dean Morgan), together with Mike Sounder (Sam Worthington) manage to find her and while Mike gets her to an ambulance, Brian waits for her abductors but winds up being shot and left for dead. Knowing that one of the killers has a cellphone from one of their previous victims Mike calls it outside the Sliger residence prompting Eugene to panic and start confessing to his mother, Lucie (Sheryl Lee). Hot words past as each blames each other, culminating in a shoot-out  with Rhino blowing away both mother and son, though not before Eugene manages to put a couple of bullets in him while a dying Lucie first slashes then stabs him with a butcher knife (leaving said blade left sticking out of his torso). stumbling outside he collapses on the porch to be greeted by Mike, who decides to stand and watch him bleed out than either call for help or put him out of his misery.

Anne, now both an orphan and only child, is left to be taken in by Heigh's family. While child murderer and cop killer Rule (Jason Clarke) is still on the run (after gunning down his former friend Levon)

Thanks Nicholas!