"Once the coroner is finished at the scene, the dead body is transported to the morgue under the coroner’s care. At the morgue, further investigation may be needed to determine the cause of death."
That's an example for a car accident. But a mass shooting would be similar.
https://www.joincake.com/blog/what-happens-when-someone-is-killed-in-a-car-accident/#:~:text=Once%20the%20coroner%20is%20finished,determine%20the%20cause%20of%20death.
"Once the coroner is finished at the scene, the dead body is transported to the morgue under the coroner’s care. At the morgue, further investigation may be needed to determine the cause of death."
That's an example for a car accident. But a mass shooting would be similar.