question about double overwatch...

[killerbot]

the other day me and a friend were playing space hulk and we got the the double overwatch bit, where both shots must be fired even if the tyranid gets killed, does this mean that it is possible to accidently kill a model you may have in line of sight behind that tyranid?

it was a cross road type thing with a termies placed and a tyranid in the middle like this
T1
T3NidT2

i was playing nids and reading the rules it sounds as though you can kill something that is behind the nid you are firing at, so does that mean that they could accidently kill thier own marine?

T1 on overwatch
T2 on overwatch
T3 on guard.

Nid moves into the middle square triggering T1 and T2 overwatch. hopefully i have explained it in enough detail to explain, i know that i have no clue about what i have just said lol :D

[AndrewGPaul]

No, because both Marines are firing at the Genestealer, simultaneously. Don't think of it as one Marine gunning it don and the other then shooting; both fire at once.

[killerbot]

but then y do the rules state that both MUST fire even if the nid is killed byu the first one. :S

[AndrewGPaul]

By "first one" the rules mean the model for which you first rolled dice. It doesn't mean that one Marine literally shoots first.

[ecurtz]

The only reason you need to roll for both is to test to see if the second marine jams.