Mister Pollack was a teacher from the Early Dawn Elementary school.
When the lights went out in the caverns, Pollack went outside to find out what was going on. When he returned, he reported that he had seen mushroom clouds all over the D.C. area. Over the following days and weeks, the adults in the cavern who ventured outside to look for help or supplies never came back, so it is assumed Mister Pollack suffered the same fate. The skeletons outside suggest that he may have died of radiation poisoning shortly after leaving.
Pollack is mentioned only in Fallout 3.