Just some of my thoughts for now below. I am going to think about it some more, and of course additional facts will start being made public to help piece it together.
Usually there are a number of variables and events which converge to cause such a horrific crime. It is not one thing.
And they won't really know how it all came to this point of course until they get into the deep weeds and talk to the suspect, look at the history, prior arrests, talk to family and friends, look at the crime scene evidence, etc.
Sometimes people think they have ideas about what happened, but then when you talk to the subject, you get some surprises.
Yes I do think this man thought he was smarter than the average bear and could get away with this crime. And yes I do think he is mentally ill and possibly using drugs. And yes he most likely suffered some sort of trigger event which caused him to go back and look at his prior victims and act out his rage and anger to one of them.
Yes any set back could be the trigger. And if there is drug abuse, this can cause serious problems in terms of judgement, and even psychosis.
So we see a man spiraling out of control.
Yes I agree, the one shot to M and two to ST is a surprise perhaps, but maybe not. This man looks like he controls his rage and anger, and stays focused on the task at hand. Puts his emotions aside and does the job. Which of course is what a surgeon is trained to do.
Also he may not have wanted a loud scene which would have perhaps alerted the neighbors or awakened the dog and children.
He is a cool number and may subscribe to the idea that revenge is a dish best served cold.
But we can clearly see he made it a personal crime. Attacking a husband and wife in their bedroom, in their bed, while they slept.
This is very personal and up close. He may have made sure MT saw him and knew who killed her. And he killed her husband too.
So it is a mixture of distance/cool headedness/self discipline, and up close, out of control personal rage.