It's a crime so unspeakable - so heinous - that even veteran prosecutors admit they've never seen anything like it before.

Isabel Martinez, a loving wife and mother of five young children, allegedly turns into a cold-blooded murderer. Cases of parents killing kids are rare, but sadly not unheard of. We've seen some horrible tragedies in the metro-area just in the last few years.

The most high-profile case involved Cobb County father Ross Harris. Last fall, Harris was convicted of intentionally leaving his 22-month-old son Cooper in a hot car to die.

Related: Parents who do the unthinkable -- kill their children

In 2015, Kisha Holmes, a former Marine, killed her three children inside their Austell apartment before taking her own life and the life of a fourth child she was pregnant with.

Also in 2015, Cedric Prather walked into his ex-wife's Douglas County house, shot and killed her and her boyfriend. Then, he turned the gun on his own son, two of his young daughter's and one of their friends. Two of the young girls survived. Prather later turned the gun on himself.

Clinical Psychologist Dr. Erik Fisher, appearing on 11Alive, said this case and the others we've seen, show a need for increased mental health help.

"We have to look at cases like this and make sure that we're getting people help in our communities that need mental health help. Because this is something that is happening often, and more often than it needs to happen," Fisher said.