  We report on the 2015 June 25 sustained gamma-ray emission (SGRE) event
associated with a halo coronal mass ejection and a type II radio burst in the
decameter-hectometric (DH) wavelengths. The duration and ending frequency of
the type II burst are linearly related to the SGRE duration as found in
previous works involving intense gamma-ray events. This study confirms that the
SGRE event is due to protons accelerated in the shock that produced the DH type
II burst.
