1.The shooters targeted US soldiers.
2.The shooters identify themselves as US enemies.
3.Therefore, the soldiers qualify for Purple Hearts.
sources:
-- "As a result of an act of any such enemy or opposing armed forces."
Dept of Def Manual: NUMBER 5110.04-M-V1, 10/26/2010: Purple Heart: Eligibility Criteria: p. 21.5.c.(1).(a).4.
http://www.dtic.mil/whs/directives/corres/pdf/511004m_v1.pdf
-- Little Rock, AK: Abdulhakim Muhammad confesses to be Al Qaeda
http://www.nytimes.com/2010/01/22/us22littlerock.html?_r=0
-- Ft.Hood, TX: Nidal Hasan confesses that US is his "enemy"
http://www.mysanantonio.com/news/local/article/Hasan-says-uniform-marks-...