What was Marques Colston Thinking?

Marques Colston of the New Orleans Saints just went full retard to end the Saints comeback in Seattle.  The Saints were on the comeback trail after scoring a touchdown and recovering an onside kick after trailing by 15 in the final minute.  
However, Marques Colston, with no game situation awareness just threw a forward pass after catching a pass from Drew Brees with 10 seconds left.  The receiver could have easily stepped out of bounds to save 7 seconds and preserve a last ditch Hail Mary attempt.
See the play below (via FOX):
colston