A Tower Controller reported a blind spot from the Tower due to airport buildings prevented the Controller from seeing a vehicle enter the runway at the same time an aircraft was landing.

Narrative

Winds were gusting about 20 to 30 kts. down Runway XX; so we were landing Runway XX. Aircraft Y came in NORDO and had called on the telephone to obtain landing clearance and requested light gun signals as well. I maneuvered Aircraft X to follow #2. I had Aircraft Z inbound from east and he was cleared to land #3. When Aircraft Y landed; he called again on the telephone to obtain taxi clearance. I hung up the phone; walked back to the strip board to pick up the light gun from right next to it. I scanned the runway and surrounding areas because I was aware that a security car had driven on the runway the night before. I visually scanned Aircraft X who was next to the runway and then looked at Aircraft Z to ensure spacing. I walked the light gun to the back of the cab and put it back where it belongs. I turned around and saw the yellow strobe lights of a vehicle on Runway XX. I scanned to see where Aircraft X was so I could send him around but they were already on the ground. Pilot was able to stop faster than normal due to wind resistance.The security vehicle then accelerated (southbound) down the runway and turned right at Taxiway 1 where the vehicle exited the field. I continued to work my traffic and then called Company A security to report their vehicle's runway incursion. Person A would not give me any information. We do not have a dedicated airport police on field. I did not initially contact the Police Department as they almost never respond to our calls. They are not deemed high enough priority. I did later contact Police Department. I spoke to pilots of NORDO Aircraft Y and Aircraft X on telephone. Both pilots stated the security car came from the east side via Taxiway 2 from between Company B hangars and Company C; which is a blind spot for the tower. We cannot see from the Gate to Taxiway 3 on that section of Taxiway 2. NORDO pilot stated that he saw the car turn off of a road in the uncontrolled section of X Apron and he must have come through the gate behind him. According to security footage; this car was on the runway in 3 seconds from the blind spot on the field and there was no way we could have warned the plane in time as they were in the flare and feet from the ground at the time. I don't know. It would be nice to have some way to view that section of the field. Maybe a camera feed in the tower cab?