To the neighbor who happened by the young man lying on the basketball court, who asked "Should we call into Police non emergency and ask for medical aid?" Yes. Make that call to 911 if you are concerned. I was walking the dog one cool, rainy night and found myself in exactly the same situation. I found a young man (teen?) lying on a sidewalk who had vomited. He was incoherent and not dressed for the cold night. I was concerned that he might be at risk of toxic overdose and of exposure to the cold, so I called 911 and asked for medical response. The 911 operator thanked me for making the call, and assured me that they do want to be called when someone's safety appears to be at risk. It's a tough call, but someone who is lying outdoors and who is incoherent, might need urgent attention for an overdose, a stroke, a head injury (our neighbor described a man with a skateboard) or some other medical emergency. It would be devastating to ignore a situation like that and later learn that a neighbor family had lost someone do to head injury, overdose (or whatever). Every minute might matter. Call 911 if you are concerned.
Call the police. It's illegal to camp there, and as you noted he was likely coming down off of a drug of some kind. Given the rash of property crimes in the neighborhood we need to react promptly to incidents like this and make it clear that Laurelhurst isn't a place to crash and that folks are paying attention.
I saw him too and did not know what to do. I did make sure he was moving, but I had my two nephews with me, so that is all I did. By the time I got back down to see him, he was up and moving on. I was planning on calling the police so that they could check on his well-being/possibly get him help. I felt sorry for him, not at all threatened and felt rotten for just passing him by the first time.
In response to our neighbor's question about how to respond to this type of incident, by calling 9-1-1 you follow the Good Samaritan Law in Washington state AND relieve yourself of moral duty (you're most likely not a medical professional who could assess the situation medically). Thanks for reporting this situation in our neighborhood and opening up a discussion of Good Samaritan Laws and First Aid Response in Washington and here are a few websites of interest with further information regarding this topic: