I just watched the video of the shooting. If the gun wasn't cycling because of the suppressor then why were there three fired cases on the ground along with three still loaded cartridges? I would think the gun was cycling just fine and ejecting the case. He fires the first round, then he pulls back the slide and a loaded round is ejected, second round fired and case ejects. Then he pulls the slide back twice in succession before a third round is fired! WHY?? Why didn't he think the gun was operating properly, is it the first time he has ever shot the gun?
A professional, not likely. A professional wouldn't have wasted the time or money to have a suppressor as he knows close witnesses will know what is happening anyway, and he would want a concealable gun that wouldn't attract attention as he escaped. A gun with a suppressor is hardly concealable! That pistol with suppressor is at least fifteen inches long!
My money is on suspect is just an insured party who thinks he was screwed on a claim by United Health Care and thinks he is "getting even" by killing the CEO.