What should I have done in this situation?

At the very least, you should have sought help of some kind.

@canidmajor From who? Should I have called 911?

You should have called 9–1-1. It’s a good lesson for the future but there’s no point in fretting about it now or feeling guilty.

I would have probably shook his shoulder to see if I could get a response. Then call 911 for medical assistance if he didn’t respond. At this point what was done has been done & hopefully you won’t ever have that same experience ever again!!!

Call 911. Knock on a door. Stop a passer by. Something.

The safest/most ideal strategy in such a situation, is to call emergency services. Not just EMS, but the Police as well.

You said you didn’t know the man, or why he was there.
You omitted details, like if it was obvious that he was homeless or if he was lying in snow.
For many reasons, I would rather a Police officer engage with the man. It’s impossible to guess how the may have acted, if you stirred him.
Speaking from law enforcement experience, you can never underestimate a situation.

He probably did need help. But. Many such characters, are approached by law enforcement and questioned. Typically. The person was simply inebriated, and once they can walk, they just need to essentially go somewhere else. They don’t necessarily want to go to detox, and start a life of rehabilitation and sobriety.
If they need medical care, they’ll get it, and probably be released from a hospital.

Sadly. You risk possibly your life, by getting involved with other people’s business.
I recently spoke with a doctor, who was shot trying to help people after a car accident.
She saw a pedestrian get hit by a car, and when she approached his motionless body, he jumped up and ran. For whatever reason, the man pulled a pistol and fired over his shoulder at the scene of the accident, hitting the doctor in hee hip and abdomen.
She was with some friends downtown, saw the accident, went to help, and ended up shot.

I’m just saying, be careful out there folks.

@MrGrimm888 was in a hot summer afternoon. His head was cupped in his hands. As to be comfortable on the cool sidewalk. He appeared to be comfortable, and I didn’t want to wake him.

I once called the EMS on a homeless man sleeping in an alcove during cold weather warnings. The homeless man just waved off the help and went back to sleep.

I have seen adults laying down in grass in shade, and asssumed that they are ok, and just trying to relax under the shade.

Also he was lying on his side. As to be comfortable.

”senior citizen lying on the downtown sidewalk, face down.” does not sound resting or comfortable.
If it happens again, get help.

In the original question you said he was lying face down on the sidewalk. In that case you ought to have called for an ambulance..

OK thanks @all. Sorry for messing up the details.

You watch TV I suppose, so you already know about 911. Right? This is a “call 911” thing.

All of us should call 911 in those cases, whether we stop or not. Reminds me of the Seinfeld ‘good citizen’ episodes.