The murder-suicide of the famed restaurateur Texas couple — which also left their two young children dead — has the former chef at their Houston restaurant reeling … and looking back to see if he missed any clues to the impending catastrophe.

If you don’t know … the bodies of 52-year-old Matthew Mitchell, his wife, 39-year-old Thy Mitchell, their 8-year-old daughter and 4-year-old son were discovered shot to death in their upscale Houston home Monday. Police say Matthew killed his family before taking his own life.

Their popular establishment, Traveler’s Table, was featured on the show “Diners, Drive-Ins and Dives” hosted by Emmy winner Guy Fieri … with their former head chef, Stanton Bundy, who tells TMZ … he’s questioning everything in the aftermath of the tragedy — including his faith.

For five years, Stanton ran the Traveler’s Table kitchen and worked alongside Matthew — who he called a great friend — and who, so far as anyone knew, loved his children deeply.

Stanton can’t even begin to imagine what could possibly drive Matthew to something so horrendous … noting Matthew was a savvy businessman, and the chef never saw the couple have anything other than a mild marital “spat” — which never got physical.

Chef Stanton — who gained fame himself by outdueling Bobby Flay on his Food Network show — ventured out on his own about a year ago … but he tells us he still talked to Matthew on a regular basis, and his best friend still works at Traveler’s Table. From what he’s heard, the plan is to keep Traveler’s Table open.

As for whether Food Network should pull their ‘DDD’ episode … Stanton says that should be up to the family, but in his opinion, it would be unfair to the other businesses featured.