At least 115 killed and scores wounded in Moscow concert hall attack

I saw cellphone video last night from inside. There were bodies strewn around the lobby. What is Russia going to do in retaliation? Putin just found out that enemy of my enemy isn't necessarily my friend. I'd like to think, with the 2nd Amendment, had happened in CONUS, It would have been over much quicker with less death and injury.
SGT James Murphy, CPT Jack Durish,
SPC Gary Welch, SGT Mark Anderson,
CPL Douglas Chrysler, LTC Trent Klug,
CSM Charles Hayden, SMSgt David A Asbury,
SSG William Jones,
SSG Michael Noll, MAJ Dale E. Wilson, Ph.D.
SGM Erik Marquez, CW3 Harvey K.
SFC William Farrell, CPL Ronald Keyes Jr
Sgt (Join to see), SSG (Join to see)