What happened in Hartford is likely an example of what is termed the "bystander effect." Each witness, perhaps confused and aghast at what they just evidenced, look at the other witnesses to see what they are going to do, assuming that the others will take responsibility. The sum result is total inaction. Ironically, this man likely had a better chance of getting help sooner, if there were only one or two witnesses present. When there exist more than two witnesses, the social phenomenon of "diffusion of responsibility" can bring about the bystander effect.
Understanding the existence of this phenomenon can help future bystanders break free from its effects. Additionally, if one finds oneself in the role of the victim, one should attempt to single out a particular bystander, by pointing to the one witness and requesting their singular assistance. Although the severity of his injuries certainly prevented this victim from making any requests, it is somewhat reassuring that at least some of the witnesses, in this case, did phone 911.