Most cases of robbery don't turn into murder, that usually happens when the robbery breaks down , or its usually planned as a murder with the attempt to make it appear to be a robbery.
There are some cases, where a victim is killed in order to steal something they have or to facilitate a robbery in a business, but those are rare
In this case, you have a victim who was at the scene by happenstance, she happened to change her shift for that day to allow a co-worker to attend a family function .
SO was it a Hit or Robbery gone wrong?
So if we are to assume that she was the intended target, it would have to be someone who knew when she personally would be there that day, this could've been someone stalking her, (which is not uncommon for some people to not disclose) someone she told that she had to work, or someone who intentionally switched shifts with her to make sure she was there (if we are assuming murder was the intention).
Police say "she had no known enemies" and speaking from experience, I can tell you that doesn't mean she didnt, sometimes, theres a lot more below the surface.
But Most likely her background was scoured by the investigating agency.
The offender walks in and shoots the victim almost immediately, police feel maybe its because he knew she sounded the silent alarm, but that is just their feeling
That's a very brash action for a would be robber to walk in kill shoot someone then to make sure the victim is dead by shooting her again before taking the time to rummage through the office, even after he knew the alarm was tripped, seems he either didnt care or perhaps indicating a knowledge, of how long a response would take.
If he was wearing a disguise, there would be no need to worry about whether or not she could describe him (if she survived) , he needed to make sure she couldn't , which leads me to believe he was not attempting to skew his appearance .
Then his movement in interesting , he looks all over before going to the register to take $200 bucks f which he seems to go to last, and stroll out of there in broad daylight in the middle of the day .
He also brings a small drawstring bag seeming to indicate he knew the haul would not be signifigant.
If he knew the alarm was tripped and the clock was ticking why not go right to the obvious cash source, the register,? most experienced criminals will tell you they don't waste time, they get what they can and get out, they don't usually waste time looking around a place for more.
Even Burglars will usually pass up big items for cash and jewelry, to get in and out fast.
In cases, like bank robberies, If they believe there is a safe etc.. which isnt as popular as the movies make it , they will need a live employee to show them and possibly access, it , but RARELY do criminals go for more, they get in and get out .
Unless you are dealing with your run of the mill convenience store robbery,which again is usually what is ever in the register, theres usually some type of surveillance done on a location where security measures are sure to be in place (banks, credit unions etc..)
The offender in this case, brings a silenced weapon, which is extremely rare, and its up in the air whether or not he was wearing gloves, what seems apparent is that he makes no attempt to hide his face from cameras
Now certainly she wasn't going to buzz a man into the store wearing a mask , however unless he was wearing a disguise, that can mean a few things 1)He knew nobody would recognize him, or 2) he knew there was not going to be a witness that could describe him to police (IE murder was planned)
Was this perhaps a first time offender who panicked ? , I personally don't think so.
In an individuals early crimes we sometimes see an overabundance of planning, beyond what is necessary to commit the crime, "fledgling" criminals are usually most nervous at the outset of their criminal career.
They'll plan, they'll practice , they'll rehearse, take several steps past the point where they need to and try to check all the boxes , and will eventually get lazier as they get more experienced, that's often how they get caught.
In this case, we see the killer shoot her almost immediately, possibly because she tripped the alarm, but why? what would that do ? why kill her ?, anger?, loss of control?, Panic? if so why finish her off? so she cant describe you to the police ?
The planning, the suppressed weapon, no attempt to hide his face, his calm demeanor after committing murder, of a non threatening female, making sure she was dead , his boldness to commit this crime in broad daylight with little concern for any chance of being interrupted, even though an alarm was tripped, in and out before police response, tells me that this is NOT a first time, but an experienced criminal.
Was this someone she knew ? my initial feeling is no, if this was someone with intimate knowledge of the office, (such as a co worker) I cant see him wasting time looking in areas where there was no money, or not hiding his face.
A police officer at least at first seems unlikely, though I cant rule it out, would most likely know about the cameras, would do more to hide his identity, that doesn't mean hes not, its entirely possible, but more so is the likelihood this is a experienced violent criminal.