Former General Barry McCaffrey, IIRCC, appeared on NBC nightly news with that supposition.  He found it unlikely that one man, even with two 20 round clips for his pistol, could have caused all 40 reported injuries and speculated that some of the injuries could have been friendly fire, (i.e. shots intended for the shooter.)  A female police officer was reported to have been the first on scene and hit the shooter with two rounds while taking wounds herself.  Dr. Hasan was reported to be in serious but stable condition and has been transferred to a different facility.  PBS had an interview with the base Muslim chaplin who confirmed that Muslim soldiers had complained about harassment due to their religion. It is going to be interesting to watch this play out.

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."