The problem with this type of scenario, though (and as we know, all the scenarios have some problem, so I'm not trying to shut down this one hypothesis) is that such an MO or profile of a predator is—only slightly exaggerating here—completely unheard-of in the history of modern criminal behavior. Nothing's impossible, but we naturally prefer a solution that has at least a couple of familiar elements. With Jason's case in the back of my mind, I've often poked around looking for anything remotely similar, but I've never even seen a mention of a case involving all these factors at the same time:
* A sexual predator who targets adult male victims
* An adult male victim who has no high-risk behaviors
* The assailant uses a sudden blitz type of method to capture the victim. It would have to be a sudden attack at some point (on the attacked-by-a-predator theory) because Jason was in a hurry. Even if he initially approached his attacker willingly (helped him with trash cans, accepted a ride, whatever) he would be expecting to continue on to the high school promptly. So he wouldn't have lingered and given the person an opportunity to, say, slip a drug into his cocktail.
As others have mentioned, adult male predators who target adult male victims, though extremely rare, are out there, as a couple prominent cases have shown. But these predators have regularly used completely different methods to capture/subdue the victim. They engage in some form of "grooming," or they at least establish a pretense or a ruse ahead of time (as Gacey made appointments for his victims to come over and do housework and so on). Dahmer met his victims out at bars and there was usually some "foreplay" (using that term loosely) before he actually attacked them.
