Last week’s deadly tornado in Livonia, Michigan formed so quickly that the National Weather Service’s radar never even picked it up.

That’s why the tornado siren wasn’t activated in the city. The National Weather Service says each locality operates and manages its own outdoor tornado sirens, some of which are activated by weather service tornado alerts.

Bridge Michigan reports that the spin-up storm developed so fast that the National Weather Service didn’t have time on Wednesday afternoon to alert city officials of the need to sound the alarms.