Kubrick photographed Alexander Singer at least 3 times in 1946 for three separate LOOK stories: People Mugging (in which the man gives the stare Kubrick used from film to film), Palisades Amusement Park, and Life and Love on the New York Subway.
I had not known who the individual might be so submitted the photos to a Kubrick group hoping that someone might help with identification. I assumed he must have been a friend. Dominic El Perro noted that on page 171 of Stanley Kubrick at Look Magazine the individual at Palisades was given as a fellow photographer enthusiast and proposed it was Alexander Singer.
I found the below photo that confirmed it was indeed Singer. The image shows James Harris, Alexander Singer, and Ruth Sobotka during the filming of The Killing.
Singer produced The Killing. He was cinematographer for Day of the Fight, and "camera and electrical crew" for Killer's Kiss.