From the photo:
(TOK-1-March 19)--SIGN OF THE TIMES-- Cambodian child plays with machine gun atop bunker as his father performs guard duty recently at Koah Oknha Tei in Cambodia. Government troops are allowed to take their families with them on forward operations. (APWirephoto via Cable from Tokyo) (ify30943str)1974
A photo from a little more than a year before Phnom Penh fell. It's for sale on eBay. Another is here.
This sums up so much about the war.
Hat tip to Khmerican.