The man who murdered the CEO of UnitedHealthcare remains unknown and at large, but the gun he used and how he used it reveal some key details about him.

On Wednesday, a masked man ambushed Brian Thompson outside a New York City hotel. He fired three shots, killing Thompson. Then he fled and remains on the run as of Friday morning.

Video of the murder (warning: it’s graphic) and a few other important pieces of evidence show the killer used an unusual setup that provides some insight into his skill level and preparedness.

One clear takeaway from the video, despite its blurry nature, is the type of gun the shooter used. While the images aren’t clear enough to identify a specific make or model for the gun or silencer, a frame-by-frame review of the surveillance footage that captured the killing shows the shooter was using a semi-automatic pistol with a silencer attached to it. The video is definitive on this point because you can see the slide of the semi-automatic recoil and cover part of the shooter’s hand after the first shot.

However, the video also shows the gun was not properly set up and didn’t function properly. The shooter’s actions suggest it wasn’t able to extract a spent casing, load a new round, and fire that round like it is designed to do. That’s why he manually racks the slide between each shot and misfire (police reportedly recovered three spent casings and three live rounds from the scene). Oddly, the shooter seems to anticipate this problem and isn’t surprised by it because, after the first successful shot, he immediately goes to rack the slide and manually cycle the gun.

That implies he must’ve had some experience shooting that particular gun with that particular silencer and understood the firearm wouldn’t cycle properly on its own. It’s strange he would use a gun he knows will malfunction, especially since the silencer doesn’t give him much of a real-world advantage.

After all, the term “silencer” is a misnomer. It’s more of a marketing term coined by the device’s inventor than an accurate description of what it does in real life. Unlike in the movies, a silencer does not turn deafening gunshots into whispers–certainly not for the 9mm rounds the shooter used in this case.

A silenced 9mm shot is undoubtedly quieter than an unsilenced one, but the decibel level is still louder than a jackhammer or an ambulance siren. The effect of a firearm silencer is more akin to that of a car muffler than a magic quiet spell. That makes sense since mufflers were invented by the same person and employ the same technique to, well, muffle the sound of a car that silencers do with a gunshot.

Additionally, the video shows he carried out this killing not just in the middle of New York City in the daytime but also right in front of somebody (who wisely flees as the shooting begins). Another person was sitting in the SUV next to where the shooting happened as well. So, if the shooter was hoping the silencer would help mask his attack, he ended up making any sound suppression moot with how brazen his actions were.

The silencer also added significant length and bulk to the gun, which makes it more difficult to conceal and maneuver. So, the silencer provided little real-world advantage and a lot of drawbacks. Yet, he used it anyway.

Outside of movies and TV, it’s rare to see a silencer used in a targeted killing like this.

Regardless, the video reveals more information. After the first shot, the attacker isn’t successful at manually cycling the gun on his initial attempt to reload the chamber. He tries to take a second shot, but the gun doesn’t fire. So, he racks the slide again and then successfully fires the gun a second time.

He then starts walking and tries to manually cycle the gun again. This time, he hits the back of the slide in an attempt to make sure the firearm is fully in battery. He is eventually able to get a third shot off before fleeing.

Modern semi-automatic pistols won’t fire if the slide isn’t fully forward. The shooter’s attempt to ensure the gun is in battery implies he has some level of training. He likely has experience beyond an introductory firearms course. He’s probably been shooting more than a couple of times.

However, most of the more advanced firearms instructors teach students to tap the magazine and rack the slide in the case of a misfire or malfunction. He doesn’t ever attempt that maneuver and, though remarkably calm, fumbles with the gun repeatedly.

Those are further indicators that he’s perhaps more of an intermediate shooter than an expert.

It turns out he was ejecting live rounds from the gun when he was trying to clear the malfunctions. So, he may not have actually needed to manually cycle the gun at some points since it was loading live rounds. That suggests that while he seemed to know going in the gun wouldn’t function properly, he didn’t have a full grasp of why that was and what the right solution should be.

Also, pictures of the live rounds found at the scene show they are full metal jackets. Most advanced shooters use those rounds for target practice because they are plentiful and comparatively cheap. However, full metal jackets are more likely to pass straight through a person, which makes them less effective for stopping your target. That’s why police and people who carry for self-defense use hollow-point bullets, which expand on impact and are more likely to impart all of their energy in the target.

He either didn’t understand that difference or perhaps couldn’t find hollow point ammo since some states restrict the sale of those bullets. Of course, some states also ban silencers–including New York. Just like the ammo, the reason he went ahead with an improperly set up silencer could be that it was all he had access to in the time he had to prepare.

While the video and other available evidence tell us the gun and ammunition he used and how he used them, it only provides limited insight into why exactly he used the gun he did or why he used it in the way he did. It doesn’t allow us to draw absolute conclusions. It just provides some fuel for speculation.

Still, all things considered, the evidence suggests this is somebody who has some firearms training. He has some knowledge of how to clear a malfunction. He has some experience with the gun he used.

But he’s also not an expert and was willing to go ahead with a gun he seemed to know wasn’t going to function reliably. That hindered his assault. However, since an armed assailant who is ambushing an unarmed victim doesn’t need everything to go perfectly to accomplish their goal, it didn’t matter much in the end.

Honestly, it feels like he’s play-acting what he’s seen assassins do in movies. Reports that law enforcement found messages written on the rounds recovered at the scene reinforce that feeling. It all seems like somebody imitating well-established media tropes of what killers do, down to the silencer and cryptic messages.