If the perp(s) are ever finally tracked down and discovered dead, I wouldn't think it's suicide over guilt or fear of discovery. I'd suspect they were finished off that same night as they'd taken NG. I don't think anyone is going to go to the trouble of dumping her in a lake; maybe in Minnesota, but not Arizona. It's too easy to hide a body in a shallow grave in the desert, or even deeper underground like at a construction site or along a pipeline that's being repaired. No body, no evidence, no chance of future confessions. While I would not be surprised if there are more people involved besides porch guy and whoever was in the house, I also don't think some foreign "cartel" is involved. Not over drugs, or her "seeing something" or whatever, but I do realize that close to the border it would be an easy story to sell, and there are people who stand to gain if that does become the narrative.
Much is being made of the "cheap" gear, the low budget almost luchadores style ski mask, that the holster didn't match the gun, and how over the top the porch guy's outfit was. Eh, maybe. When I look at it I don't think "cheap" I think umbiquitious; he's not shopping for exclusive, easily traced bad guy gear at the Super Villian Store. Assuming he's buying his outfit "off the rack" rather than at Goodwill or collected piecemeal at garage sales, Walmart is the largest retailer in the world. It's like hiding in plain sight. LE says "we're looking for this specific backpack" And Walmart kinda hems and haws and says "Um, yeah, we sure do sell a lot of those..." Can they track it? Probably not. Can they even determine if it was bought locally? Again, probably not. This guy went to the trouble of running a dress rehersal to test the camera in advance of committing the crime. I don't think he's a burgular, nor is he an opportunist who heard about some little old lady who pays in cash. *She* was the job. Abducting her while making it clear that she did not just wander off was the point. Leave just enough blood to let people know you're willing to hurt an old woman, but not enough that they think she's already dead, at least not right away. I do not believe that anyone involved in her abduction ever had any intention of collecting a ransom, or of returning her. As they say, MOO.