In the center of the picture at middle distance you can see a cloud of grey smoke. A tank has just hit a big mine and the explosion killed SP4 Anthony J Marinelli, the driver.
This picture was taken 26 June1969 by Bob Forman from inside the 5/4 Arty battery firing position at LZ Saigon. On the right is one of the 155 SP guns of the battery. The hills (?) in the background are in Laos and guard the Ho Chi Minh Trail.