Server Players spawned in same place on my server. Were stuck and TK'd?

Not sure if this is a new exploit but the players seemed to spawn in the same place and were stuck together and they said another played killed them the beginning of the first wave; I heard a grenade go off after spawning for the first wave and it said they blew up so I thought they just killed themselves. Friendly fire is not enabled on my server; it has the antiblock, ServerExt, and kill message mutators installed. I saw them spawn the next round and they were all mashed together in the same spot and they said that they could not move and were eventually killed by specimens.

The guy they said team killed them left the server after they all died so that seemed kinda suspicious.