Revealing the details of the attack the police said a van used had been fitted with a single improvised mortar tube and contained home-made explosives.

BBC: Two released in dissident operation

The mortar round exploded in its firing tube during the exercise, said Brigadier General Jim Lukeman at a news conference at Camp Lejeune.

NPR: Mortar Explosion In Nev. Kills 7 NC Unit Marines

Both young men were among seven members of the 2nd Marine Expeditionary Force killed late Monday when a mortar shell exploded in its firing tube during an exercise at Hawthorne Army Depot in Nevada.

NPR: Marines Killed In Training Were Young, Lives Ahead