Cigar shape ufo with gateway

My parents had started leaving my brother and I alone as I had recently turned 16 a few months before and had my own car.  They were away for the weekend and my brother and I were awakened by a loud rumble which was almost causing the house to shake.  It was a sunday morning and the date listed above is approximate as this was a long time ago.  We both ran to different windows in the house looking to see if we could find the cause of the rumbling when we looked out the eastward facing windows we saw a large cigar shape craft at least 200 ft long heading slowly from south to north towards a glowing triangle shaped doorway (for lack of a better word) with the rumbling and shaking being very loud, when it got to within a few hundred yards of the triangle it shot into it at incredible speed and the triangle collapsed on itself closing like a iris of an eye.  Then complete silence nothing dead quiet, we stared at each other and said what the hell was that he said no bodys gonna believe us if we tell em.  We told our parents and they didnt believe us, still dont.  I waited years and we felt it was time to at least report this as i have never heard of another report like this
Witness indicates that the date of the sighting is approximate.  PD