The shooter apparently hit the victim once in the back, once in the leg and also missed a shot. He was extremely close to the victim - 1st shot from maybe 10' and last shot from maybe less than 25'. This is very indicative of a novice. For perspective, at the range this week I was hitting 10/10 shots with pretty quick/rapid firing from 25 yards to an @20" target. I am only a moderately proficient shooter.
The shooter's gun jammed repeatedly. Again, evidence of a novice. It takes a decent amount of neglect for a standard semi-auto to jam. For perspective, I lazily didn't clean my firearm after the last several uses months ago. The firearms sat in my safe for months. I went to the range # times this week with my son (entering the armed services and practicing) and lazily didn't clean it after each use. Only at the 3rd session did the gun start to malfunction from being dirty. A professional would never neglect their weapon like this.
The weapon seems to have some sort of appendage added to it. It is really hard to tell from the video but that pistol is abnormally long. Long slide pistols do exist but ... it isn't standard. Why would a professional have / use that for a close range shot in an urban setting where he needs to be mobile? Makes no sense. So maybe a silencer has been added? Contrary to what the linked video above says, silencers are not illegal. They are hard to get and you have to go through a protracted approval / registration process, but they can be had. A professional hit man would not follow those rules. It is also the case that homemade silencers can be built. Maybe that's what this is?
The bullets reportedly had the words "delay", "deny", "depose" etched into the casings. Weird. Why would a professional do that? Let's call it another clue toward not a hitman.
The shooter knew how to clear a jam and did it multiple times quickly. When my firearm jammed my son - complete novice - had no clue what to do. I was able to clear the jams but it wasn't always easy like in the video. So we have evidence of a shooter with advanced gun familiarity.
My guess: a disgruntled consumer (etched words about insurance claims) who has an abnormal gun familiarity (cleared jams, possessed/built a sound suppressor) but who isn't a professional (potentially dirty gun, missed easy shots).