At approximately 9:40 pm: on thursday july 20, 2017, i was returning from dinner in the village of la mesa. my transportation van was in the shop for servicing and i was using a motorized wheelchair. my daughter and son-in-law and accompanied me in my daughter's truck and were playing leapfrog sure that i had no difficulty because of the darkness. there were no streetlights in the area. i was using a strobe headlamp so that oncoming vehicles could see me. as i turned from i highwood street onto wetherly street i became aware of the flashing white light approximately 50 yards behind and above me and there was absolutely no sound. i live in the area within the flight path of commercial aircraft approaching landing at lindbergh field in san diego. i thought at first the lights were landing lights of the commercial but noticed there were no navigation lights; just three white lights blinking at the same time. i assumed they were navigation lights, but the craft was too low to have been a commercial aircraft and the was no sound. i am quite familiar with jet engine, helicopter, and reciprocating engine sound and noise. because everything was silent, i stopped momentarily to listen. there were no sound of any kind, human, animal or any type of aircraft. the craft was now directly overhead but it was so dark i could not make out any shape except for the three lights which appeared to be at the points of a triangle. the craft was moving only slightly faster than i. i increased my speed as much as possible and continued up wetherly street. the craft continued above me and moved slightly faster. i estimate i was moving in about 5 to 8 mph. i stopped a second time to listen for any sounds. there were none. as i approach my driveway my daughter had moved her car onto the driveway and sheen and her husband got out. i have a motion sensor light in the driveway which came on at that point. in a normal voice i asked my son-in-law and my daughter if they've heard anything. they both said no. everything was silent in the craft and continued easterly direction and disappeared behind some trees in my neighbor's yard. i called the la mesa police who were unable to verify any savings by their personnel.