The First 48

Homicide detectives rely on social media messages to find those responsible for killing a 17-year-old victim in Mobile, Ala.

When a home invasion leaves a father-to-be shot dead, Detective Dianna Baumann's only hope for answers is a suspect fighting for his own life. In Atlanta, two brothers are found shot dead in their home leaving Detective Scott DeMeester with little to go on, when his only potential suspect suddenly wants to talk. When a man is shot dead inside a boarding home, Atlanta detectives try to drum up a lead from a roommate involved with the suspect. The life of a 19-year-old woman hangs in the balance after walking in on an intruder in her home. When Tulsa detectives find the suspect, they realize it's not the first time they've stood face-to-face.

A surveillance camera on a Minneapolis bus captures a shooting outside a church. The footage leaves detectives wondering if the shooter acted in self-defense. Surveillance cameras at a Minneapolis convenience store capture more than just the shooting. Footage suggests vital DNA may have been left in the store by the shooter himself. Then, surveillance footage in Atlanta shows a man carrying a box moments before he is shot. Detective Tracy Casey must determine if the box's contents holds the key to determining motive. Additional Minneapolis surveillance cameras capture the shooting of a young man in the Cedar-Riverside neighborhood. But detectives need the help of the Somali community to identify the shooters in the video.