Just before New Year's, a hockey mom is gunned down at her front door; later that night, seven more bodies are found in another suburban home; police discover a shocking connection between the two crimes as they track down the killer.

After a family is found massacred inside their Santa Claus, Georgia home, the hunt for their killer hinges on the eyewitness testimony of the three young surviving daughters.

Just before Christmas, the body of a young mother is found strangled inside a burning car in a quiet Minneapolis suburb and detectives suspect that she was killed by someone very close to her.

Just after Christmas, a young couple is found murdered inside their Florida home; neighbors can't imagine the couple had been in the area long enough to make a mortal enemy; police uncover deeply personal details, and soon expose a deadly secret.

A beloved couple is found murdered inside their home on Christmas morning; a single palm print is left behind; investigators work tirelessly to match the print to a suspect, until a letter from prison takes the case on an unexpected course.

A holiday is ruined when a couple is gunned down in their bed during what looks like a brutal home invasion, but police soon discover the true motive for the double homicide is a shocking tale of deception and betrayal.

On Christmas Eve in a quiet town, elderly couple Bob and Idella Young are brutally slain at home; a bloody glove found at the crime scene has the killer's DNA, but no one matches the sample.

Two days after Christmas a mass shooting terrorizes a small town; after killing two people and wounding many more the gunman is taken into custody; when police search for answers they uncover the worst family massacre in US history.

Firefighters respond to a house fire and discover three gunshot victims inside; authorities pursue the heavily armed murderer through Christmas.

The holiday season screeches to a halt when six members of the Anderson family are discovered to have been gunned down in their home; detectives work closely with family friends to track down the shocking murderer.

The Ortega family's annual Christmas Eve party is destroyed when a man dressed as Santa, wielding handguns and a homemade flame-thrower opens fire; detectives are led down a terrifying path that leads them to a sociopath.

When a mother and her two daughters fail to show up for Christmas dinner, officers enter their home and discover all three have been shot to death; the search for their killer reveals an unthinkable family nightmare.

New Year's in a tiny town, Joanna and Carl Dutcher ring in the year with their grandson, days later, they are found violently killed; the hunt for the killer leads police to a sinister group that threatens the entire community.

A woman is shot to death while driving her sons home from a Thanksgiving celebration; the hunt for her killer leads to an unlikely suspect, making investigators realize her murder is not as random as it seems.

Earl and Terry Robertson are found brutally murdered in their home just before Thanksgiving; investigating whether this is a holiday robbery gone terribly wrong, or a crime committed by someone the couple knew and trusted.

A deranged shooter attacks a family Thanksgiving dinner, leaving four dead and even more wounded, setting off a massive holiday-season manhunt to catch the killer - before they can strike again.

Telling the twisted stories of some of the most maniacal siblings in history. Through exclusive interviews and firsthand accounts, the series will delve into the evil minds of siblings who partnered together to commit some of the most heinous and sophisticated homicides.

Each episode of this true-crime reality series examines a different felon, usually a female, who has committed murder or attempted murder. The victim is usually the perpetrator's partner. The documentary-style series features interviews with friends and family members of the accused and victims, law-enforcement officials, attorneys and other people with first-hand knowledge of the cases.

There are manipulators in the midst, scheming right under everyone's noses. Even with people trusted the most, there may be something sinister lying beneath the surface -- a plot set in motion by someone close with a deadly motive. This true-crime series tells stories of actual murders committed not by strangers but by someone the victim knew, someone hiding in plain sight, or someone leading a double life. These wolves in sheep's clothing use deception as a weapon to try to get away with murder.

Emmy-winning investigative reporter Chris Hansen brings his journalistic skills and criminal insight to this newsmagazine series, digging into the depths of unlawful behavior and bringing life to some of America's most chilling, heart-wrenching homicide cases. Mirroring his breakthrough reporting for "Dateline NBC," especially exposing hundreds of sexual predators who targeted teenagers online, "Killer Instinct" harnesses Hansen's passion for uncovering the truth and shedding new light on homicide cases. Using access to key witnesses, loved ones and law enforcement officials, Hansen deconstructs the cases before putting pieces back together. He adds insight drawn from visiting crime scenes, interviewing key players and uncovering archived material.

On the outskirts of Los Angeles lay the city's roughest neighborhoods, the stomping grounds for LAPD Detective Lindy Gligorijevicin in the late 1990s. During that time, the police department's Foothill Homicide Unit investigated hundreds of murders, but only Gligorijevic -- driven by the need to give victims a voice -- earned the moniker "the killer closer." In this series, she revisits her most shocking cases, detailing how she solved them and the ways in which she convinced cold-blooded killers to confess.

Most true-crime shows let viewers know the identity of the victim right away, before working their way into revealing the identity of the perpetrator. That's not how things work on "Killision Course," which conceals all of the participants' roles until the episode's final act. While working toward the conclusion, each hourlong episode re-creates a murder case involving a victim, accomplice and killer. Stories often involve friends or lovers who commit crimes against people who once trusted them. It's all part of the road leading up to the big reveal, which is when viewers learn what role each party played in the fatal act.

"Relentless With Kate Snow" takes viewers on an emotional journey with grieving families as they work tirelessly, often putting their own lives in danger, to find the culprits responsible for the deaths of those they loved most. Their relentless pursuit of justice paired with the opportunity to work alongside law enforcement creates a powerful and dynamic force that won't rest until due process is served. From a mother dedicated to putting her son's killer behind bars after he's gunned down at a recording studio to a 20-year search for a victim's killer that was so aggressive it transformed an unsolved, cold case into an active investigation, the series reveals gripping firsthand accounts from the families who will stop at nothing to get the justice the victims deserve.

Hundreds of homicide cases in any given year can shake even the staunchest cities and police departments to the core. The statistics, however, don't paint the real stories and the effect that lingers -- through the pain endured by victims' loved ones, the community impact, and the memories that detectives will never forget. "Homicide City" explores unforgettable murder cases from major American cities, investigations that had law enforcement banding together across metropolitan landscapes in a sequence of manhunts. Each story is told by veteran homicide detectives, local reporters, and the victims' families.

Retired NYPD Detective Kevin Gannon questions if the country's most notorious string of mysterious, accidental drownings are accidents or homicides and wonders if they could all be connected to The Smiley Face Killers.

Some of the world's most notorious murders are the subject of "It Takes a Killer," which investigates the crimes from the perspective of the killers, trying to get inside their minds and determine their motives. Leading homicide investigators and experts from such agencies as the FBI and Scotland Yard take a look at the evidence pulled from crime scenes and profile the killer's behavior to try to piece together the details of each murder, explaining when, why and how each criminal committed the crime. For the wannabe detectives watching the show, the experts also reveal how the crime was solved -- which often requires authorities to think like a killer.