Shishio knew that most of the living weapons that were developed in the past were created by Deva and thought that this Deva might become a human enemy in the future. He then shook his head and wouldn't cross the bridge until he came to it so he didn't think too much until he saw Deva.
(AN: Btw he took a bath in a river so there's no blood on him or much dirt if any one is curious. I didn't really wanna talk about something as boring as that and waste time for the readers.)