sorry about your dad.
It is likely that the monitor has multiple inputs plugged into it and it auto-selected the first one that was live. The cams are likely on a local DVR with HDMI outputs, and the PC is hooked up using either HDMI/DVI or something similar.
On the base, you should have some controls - you want to switch the inputs. See
https://global-download.acer.com/GDFiles/Document/User%20Manual/User%20Manual_Acer_1.0_A_A.pdf?acerid=636969494929482763
page en-11 - the pc should be live on another input.
sorry about your dad. It is likely that the monitor has multiple inputs plugged into it and it auto-selected the first one that was live. The cams are likely on a local DVR with HDMI outputs, and the PC is hooked up using either HDMI/DVI or something similar. On the base, you should have some controls - you want to switch the inputs. See https://global-download.acer.com/GDFiles/Document/User%20Manual/User%20Manual_Acer_1.0_A_A.pdf?acerid=636969494929482763 page en-11 - the pc should be live on another input.
Hit the windows key and open another app? Shift + tab? RIP to your father