Assassin question

[Misery]

Ok, very simple question here:

Are assassin squads on the solar map supposed to randomly burst?  I had one sent at me from the Acutians, but it travelled about 2/3rds of the way there, and then.... exploded.  Not for any apparent reason.

Hardly any time later, maybe 20 seconds or so, the Evucks send one after me, which also randomly pops.

Might this be a bug, or is there just something I'm not aware of? 

[Orelius]

Sometimes, when assassins enter the space of a race that is particularly friendly to you, they kill them for you.  I think that may be why.

[Histidine]

Sometimes, when assassins enter the space of a race that is particularly friendly to you, they kill them for you.  I think that may be why.

Although then the question becomes "How did Misery miss the event log detailing this?"

Unfortunately assassins only seem to come for me during the post-mission fast forward, so I haven't had an opportunity to observe the apparent bug myself.