been avoided. justin valdez, seen in this youtube video honoring his family, was shot in the back of the head as he exited a san francisco train by a man who flashed a gun several times in front of distracted gadget-absorbed commuters. >> my brother was innocent and there was no reason for him to be killed. >> reporter: surveillance video of the incident hasn't been released with the exception of these images of the 30-year-old man police say shot valdez. authorities say the rest of the footage shows him pulling out the gun several times in front of a dozen commuters including valdez who had his back to him but no one on the train noticed. >> you can see people sitting or standing around him. they are busy working with their tablets or smartphones. completely distracted. >> reporter: police say, it was completely unprovoked. that the