Yep, what one could expect if instead of starting working as a mercenary - one would just waltz off away from the company, right after arriving to one's area of service, and be away for days if not weeks. They'd think all sorts of things - that one is a spy or saboteur, and will indeed shoot on sight.
That said, getting sonocaster itself won't make the Camp hostile - just gotta go get it after doing a few quests for the Camp, once they say one is free to go around. I think at very least two Camp quests plus 1st Camp defense are to be done, but may be a few more - memory hazy.
