I've experinced with a 911 center, long time ago, when I was working on the computer in my living room, I heard a shot fired 4 times in the back of apt or under-pass freeway bridge (before start construction of city train system). I turned off my answering machine and dailed 911, press a space bar several times till a "TTY detector" detected my tty tone, it's start communicating. "Minneapolis 911 Center, what's your emergency? ga" (the Minneapolis center covered hennepin county area), I typed "Shot fired in my area, can you please send the park ranger or police to check the area either parks or under-pass bridge near my home (address)." the 911 operator told me, they received a 7 calls in my same area about shot fired. Now this year the new technology system called "Shotspotter" in my city. when someone shot fired, the shotspotter system will automatically electronics to all onboard computer squad cars to get pops up on the screen, and they caught a shooter, that where shotspotter scanned a gunner hidden in the area.
I like a shotspotter detection system, it's very helpfully police can find a shooter in the area.