Actually, I'm a little confused as to what exactly went down myself, since I didn't know the 3rd were on Macharia...and yes, I've heard of the 3rd facing down a huge horde of WE's. Got quite a few conflicting reports, to be honest, but maybe they had vanquished the WE's and moved on? One source said that they were facing off against Grandfather Nurgle's legions, and were decimating their foes when Abaddon turned his Planetkiller on Macharius, perhaps because he thought destroying an entire company of some of his most hated foes was more important than facing a 'possible' defeat. Also, I haven't read anything 'official' on this from GW either, but so much has transpired that there are many things that have happened (that I know, did actually happen) that GW may not have had time to pay proper tribute to this tragic event. In any case, there are many reports of it from www.bolterandchainsword.com. Look on any of the 'Eye of Terror', 'Amicus Ades', or 'Blood Angels' forums, and you will see many an enraged angel of death.