key out, truck still running

I did search first, but found nothing. The other day when I got back from errands, I pulled in the driveway, put it in park, turned it off and took out the key. I noticed when I opened the door that the truck was still running!Got back in, put it in reverse, then back in park, then it shut off. 2 days later, it did the same thing, only this time it shut off when I opened the door.
The only recent work done has been a tranny rebuild.The aftermarket remote start/keyless entry was on the fritz after it came back from there. Now it's working again. It started working in between the 2 episodes mentioned above.
The multi-function switch is clicking away, so I keep the radio up louder, which is why I didn't hear the truck still running both times.
I mention this only cuz I don't know if it has anything to do with anything, and want to give as much info as possible. Does anyone have any suggestions on where to start looking?

My guess is, it's posible the remote start module has gone bad, or it could be the igition switch going bad. Chevys are known for that. I'd start with disabling the remote start.
SC

if the engine keeps running hit the brake pedal, if it shuts off it might be the remote start unit because they are supposed to shut off (if no key) if the pedal is hit