Use these sources.
https://www.firerescue1.com/fallen-firefighters/articles/study-more-firefighters-died-by-suicide-than-in-the-line-of-duty-in-2017-bSXUHJIWgOtMQCcU/
https://ps.psychiatryonline.org/doi/10.1176/appi.ps.201500177
https://pubmed.ncbi.nlm.nih.gov/21890054/