DNS, the shooter was fleeing the restaurant where he had just randomly shot three people and all other targets fled. That area is a small collection of restaurants, parks and jogging trails next to a lake that serves as a reservoir for the city. The entire area is packed with people usually and you can walk easily from one bar/restaurant to the next. You can see the environment here:
https://www.google.com/maps/place/L...2!3m1!1s0x87b21b0ceeec2c95:0xbb2717c2769d58fd
So, I disagree with your assumption that the “shooting was over.” Given the circumstances, I think it reasonable, and probably prudent, to assume the shooter was merely looking for additional targets rather than fleeing the scene.
Also, if we are going to be very pedantic, a mass shooting as defined by FBI did not occur because only three people were shot before the shooter was killed. To the extent the armed citizens stopped him from shooting more people, they did in fact stop a mass shooting, even though they weren’t successful in stopping the shooter 100%.
ETA: According to this report (
https://www.themaven.net/bluelivesm...-armed-citizen-heroes-f0At5d0v00SEQYEfGVnBBA/), the shooter opened fire from the doorway of the restaurant into the restaurant. The two men who shot him were inside the restaurant when it began, escaped, got pistols out of their vehicles, and returned.