[null and void]

The radius of the burst is approximately 6 meters, but fragments of the plastic body occasionally fly as far as 27 meters. Effective portions of the agent may be carried as far as 75 to 100 meters downwind. Personnel using these grenades should wear protective gas masks.

The tent is probably no larger than 3 meters on a side. I bet the men weren't sleeping in gas masks...

[Cvengr]

It might not have been thrown inside, but adjacent to the tent, or it may have been a pyrotechnic device colloquially referred to as a thermite grenade. There are also other illumination devices other than thermite. The term gets bantered about a bit liberally by the infantry as discerned from high explosive or fragmentation grenade.

[DB]

It isn't a bomb. It takes time for it to get going. It is to destroy equipment not people. People would simply run away. Nasty fumes doesn't mean death.