For the APView logging of messages, as specially the shutdown, you can find the information in the out.deb log file.
1) Find message containing "op:KEY(kill_xc)". For example:
16:48:58.183 S1 P4420 T5540 C=3 Task=27 RMW OUT: (rmw_menu,1000,I) vw_id:35, op:KEY(kill_xc)
2) Take a note of the vw_id value, which is Remote Viewer ID of whomever issued the command - in case of this example it is 35.
3) Find message containing "Connect 35". This message also contains username which is used by Remote Viewer with ID = 35:
16:48:50.917 S1 P4420 T2564 C=0 Task=18 RMW OUT: (rmw_packet,600,I) Connect 35 firstname.lastname@example.org
In order to have these messages displayed inside out.deb file. It is necessary to have "Information messages" ticked on in Expert Interface/Infrastructure/Debugging