C172 pilot unknowingly landed at a closed airport in order to secure an aft baggage door that had opened in-flight. Encountered equipment and a person on and about the runway on his subsequent takeoff.

Narrative

Shortly after passing north of an enroute airport; my rear cargo door opened. Because of this I diverted to a nearby airport to secure the door and refuel. This airport was not listed on my route of travel because it was South of my planned route. Because it was not on my planned route I did not receive any information/NOTAMs regarding it during my preflight briefing. Using CTAF; I used standard pilot position reporting methods while approaching the airfield and entering into position. While on the 45 for Runway XX; I noticed that there was heavy equipment near the runway. When I entered down wind; the heavy equipment pulled off to the side. There was never any equipment on the runway while I was in the pattern or on the runway. I landed without incident; refueled and secured my cargo door. While doing that; a resident pilot came up and mentioned that the airfield was closed. We both noted that there were no markings on the runway to indicate that it was closed. For safety; I opted to takeoff on Runway XY. I did this because the equipment was on the far end of the runway (I would be airborne long before reaching them) and the winds were constantly out of 290. While checking the flight systems from behind the hold short line I noticed the equipment moving away from the runway and stopping so I believed they saw me preparing for takeoff. I transmitted my normal takeoff report; 'Cessna Y taking off Runway XY departing to the east.' No response was heard so I commenced with my takeoff roll. While part way through my takeoff roll at approximately 45 IAS an individual on foot near the end of the runway walked out onto the runway. Upon seeing my aircraft on takeoff roll; he quickly moved off the runway. At no point was he/she flagging or making any hand motions; it appeared as though he was just standing there looking around. I had a normal takeoff and would estimate my altitude to 400 to 500 FT AGL when passing over the equipment and pedestrian. I later confirmed with flight service that there was an active NOTAM for the airport listing it as closed.