Good detectives look at a crime from all angles, so we should too.
What if these murders and the 2008 murders had nothing to do with each other?
What if the murders had nothing to do with Dr. Brumback's work or the university?
What if Dr. Brumback was not the prime target but Mrs Brumback was?
We have no word from LE that the two incidents are connected or that the murder of Dr. and Mrs Brumback were related to his work, so we should not get stuck on these possibilities however likely they may seem to be.
What do we know about Mrs Brumback? Was she working? Did she have enemies? What kind of person was she?
I find it odd that two weapons were used. Maybe there were two killers?
Stabbing is so much more personal, and also more risky. The victim might scratch the perp, or knock the knife out of his hand, the perp will most likely get blood all over him, making it more risky to leave and be seen like that.
It could be that the knife was just a backup and shooting both had been the plan but the weapon malfunctioned - maybe that's why the clip was lying on the floor?
In any case, this was a messy crime. Evidence was left behind and at least one person most likely fled the scene with blood on his shirt.
To me it looks almost as if Dr Brumback was instantly silenced so he would not be able to interfere when the perp or perps were doing what they had come to do - to get something from Mrs Brumback?
Just throwing some thoughts in. Just moo.