When Victor bemoans the passing of Dr. Rasmussen, he suggests that the doctor may be awarded a posthumous Nobel Prize. Now in all of history, only four have been awarded, but only to those who were nominated before they died, then passed away prior to receiving it. Other than that, no Nobel Prizes are awarded posthumously.
No explanation for how the guy could have gotten the gun for the frame-up.
No justification for McCall going in alone, rather than wait for the backup that was on the way. She knew where the suspect was and what he'd already done there, and had no means of escape. Unnecessary risk to take.