Don’t jump to conclusions. It sounds like it may have been a weapon malfunction.
An apparent in-bore explosion of an M777A2 — a new lightweight howitzer cannon that fires 155mm artillery rounds — occurred during a live-fire exercise, injuring eight Marines and two Navy personnel, The Fayetteville (N.C.) Observer reported.
That’s the trouble with the M777 - the measures taken to make it so lightweight also make it seriously unstable when firing. If you thin out the thickness of the bore to reduce weight, you take the chance of the bore blowing apart when subjected to the pressure of the gases releases when the poweder is ignited. This was a major danger to artillerymen for centuries and is why the traditional color of cannoneers is red (blood) and why St Barbara is their patron - those who fear a sudden and violent death.
I hope there was no individual malfeasance so those involved can continue serving our nation.
Also surprised to learn that this howitzer is only 1/2 the weight of the weapon it replaced.