Tootles
Deceased RIP
I had no reason to doubt his story .
Sorry Cobweb, but I have. Natural curiosity would make one look at just what this 'hissing cannister' actually was, even if that survey was left until the morning, and even maybe retaining it for further inspection. A small cannister as described was either smoke, or an irritant, such as CS? Anything else would probably need a cannister as large as a gas bottle!