SM-T810 stuck in "D/L- do not turn off target." Flash stock rom to fix?

On my rooted T810 I mistakenly hit restart through Knox and ended up in Odin mode. If I do Power + Volume Down it'll show the Samsung logo for a second, then immediately go to "Downloading...do not turn off target." Other key combos like recovery mode don't seem to work for me (unless I'm doing them wrong). What should be my plan from here? I'd like to unroot at this point, so try to flash a stock rom through Odin?

Thanks for the help.