Julie and Parker Schenecker
04/20/2011 AT 07:15 PM EDT
Colonel Parker Schenecker was deployed with the Army in Qatar when he got the unthinkable news: his children – Calyx, 16, and Beau, 13 – had been shot to death
, allegedly at the hands of their mother, Julie.
Since the shootings, Schenecker has struggled to move forward from the tragedy.
He also has not given any interviews about the crime, but agreed to talk with PEOPLE as a way to honor his children and to set the record straight. Sitting in the living room of his home, just a few feet from where his children were found, Parker Schenecker, 48, explains how Julie's depression led to the unthinkable crime.
"We were a typical American family," he says, "but we had a sick member."
Schenecker says that his wife had suffered from depression since before they were married. "It was a chronic mental illness that we've been dealing with for 20 years in the family," he says, "I never had any indication that she would harm the children, or that she would ever think of taking the children's lives. It was absolutely incredible when I found out she did."
In early January, Schenecker followed military orders to spend two weeks in the Middle East. "I didn't have a choice," he explains. "If I don't do my job, I get fired. I get put in jail."
Although Julie Schenecker was treated for depression and bipolar disorder, she did not share the details of her treatments with her family. "Because of HIPAA [Health Insurance Portability and Accountability Act] laws, I had no access to her medical records at all," he explains. "I didn't know what was going on."
After he suspected that Julie had substance abuse issues last November, Schenecker convinced her to check into inpatient rehab. "I did everything I could think of to do," he says.
Three months after the killings, Schenecker still tears up as he remembers Calyx and Beau, whom he calls "typical American kids living exceptional lives." The home remains full of constant remembrances of the teens: Calyx's artwork and Beau's soccer trophies.
"They make me miss my kids more every single day," he says. As for his relationship with Julie – whom he is divorcing
, Schenecker says: "I don't hate Julie. I feel for her. I'm going through my hell; she's going through her own hell."
For Schenecker's full interview – including never-before-seen family pictures – pick up this week's issue of PEOPLE, on newsstands Friday