Triangle shaped object with flashing lights, Hammond Indiana ( Hessville ) 1966 or 1967

It was Xmas vacation time, as I was 13 or 14 years old at the time. The year was 1966 or 1967. It was dark outside, evening hours, I looked out the front window and noticed a triangular craft, approx 6-feet in diameter with blue, red, and white flashing lights desending downward, stopped and hovered in the air approx 50 feet. I ran and got my father to witness. When my father arrived we saw the object start to slowly gain altitude, and the fly away east on a sharp angle, gaining speed until it was out of sight. Dad and I to this day can not imagine what this object was.
Witness indicates that the date of the event is approximate.  PD