CHICAGO (AP) — Chicago’s police chief has put into writing a threat that officers could be fired if they don’t comply with the city’s COVID-19 vaccination policy, adding that those who choose to retire rather than adhere to the policy might be putting their retirement benefits at risk.

In a memo sent Sunday night, Chicago Police Superintendent David Brown said that those officers who do choose to retire rather than comply “may be denied retirement credentials,” the Chicago Tribune reported.

As it has done throughout this dispute, the Fraternal Order of Police posted instructions on its website about what officers should do if given a direct order to report on the city portal their vaccination status. This time, it posted a letter that officers can sign and present to their superiors.

“Complying with this INVALID order and the violation of MY Bargaining, Constitutional and Civil Rights has furthermore caused me severe anxiety while challenging both my religious and moral beliefs. I am in fact complying with this because I am being forced to do so under complete duress and threats of termination,” the document on the website reads.

This follows instructions that FOP President John Catanzara posted on the website with advice that includes using body cameras to record orders to report their vaccination status.

Brown’s memo is not a surprise. On Friday First Deputy Eric Carter said officers who refused to meet Friday’s deadline on reporting their vaccination status could face discipline as severe as termination, unless they have an approved medical or religious exemption.

Also, late Friday, a judge granted the city’s request for a temporary injunction barring Catanzara from making any public comments that encourage FOP members to disobey the city’s COVID-19 vaccine mandate until the next hearing on the city’s lawsuit on Oct. 25.