This is a second hand report. I myself did NOT witness this. my grandfather, grandmother and aunt witnessed a ufo flying low so that it was clearly visible. Further, the "entire" neighborhood of medina in the town of Isabela emptied out of their homes to observe the craft.

My grandpa is now deceased, grandma has alzheimer's and my aunt is loathe to admit it- though she has admitted to a few family members, including her children.  also my father attests to the veracity of the story.  
Publicly, my aunt would NOW say she assumed it was military--however the description fits the classic saucer shaped unidentified object with pulsating color lights.  By that time Base Raymond of USAF in neighboring Aguadilla was closed.  Further Isabela has had a reputation for UFO & USO sightings.
Source of the report elects to remain totally anonymous; provides no contact information.  PD