Strange aircraft manuver at night

I was 8 at the time,I was visting my aunt and uncle for the summer.
We were driving back from a friends house,approx around 11:00,it was dark.We all noticed a low flying aircraft flying in the distance,all we could see were what we thought were aircraft running lights.(but now thinking back there were too many off them and the outline of the lights formed an oval or saucer shaped object..)  my aunt pointed it out..We really didn't give much thought about as we drove along..that is until the aircraft did an immediate 90 degree turn down and then another 90 degree turn that leveled the aircraft right above the tree line,never reducing speed..the aircraft disappered over the tree line.
We all thought that was strange as we've never seen an aircraft perform a manuver like that, low to the ground and at night.
Witness indicates that date is approximate.  PD