MONTGOMERY, Ala. (AP) – An Alabama inmate scheduled to be put to death by lethal injection next month says the state lost the paperwork he turned in selecting an alternate execution method.

Fifty-seven-year-old Alan Eugene Miller is set to be put to death Sept. 22 for a 1999 workplace shooting rampage that killed three men.

When Alabama approved nitrogen hypoxia as an alternative execution method, state law gave inmates a brief window in 2018 to select that as their execution method.

In a federal lawsuit filed Monday, attorneys said Miller turned in a form selecting nitrogen, but the state now says it has no record of that.