CNN is reporting that it’s the Russians.
Hasn’t there been a rash of these situations? I read it reported and then no follow up.
UPDATE:
Redstone Arsenal: Lockdown lifted, ‘potential active shooter’ incident under investigation
http://www.al.com/news/huntsville/index.ssf/2017/06/emergency_situation_reported_o.html
Imagine an arsenal not able to return fire.