The actual shooting (in which two people were wounded) did not take place at Fort Detrick. After the shooting, the shooter drove to Fort Detrick and was killed there.
I'm leaning toward either domestic incident, or love triangle. Looking for more information. So far, what I have is that two people were wounded (seriously) at a business park near the base. So the incident is not a "mass shooting" or a "mass murder," irrespective of how much the mass media disinformation machine tries to promote it as such.