Contractor Killed My Pets

I am besides myself and don’t know what to do moving forward. we paid over $5,000 to our contractor and some guys he referred to build a shed on the side of our house for our Chinchillas. we wanted them to have their own temperature controlled space. Paid extra for the insulated shed as well as adding about half a foot of insulation on both sides of the shed and putting in a portable AC that our contractor assured us was safe. we had them add a platform to put the AC on, vent it out the shed and even after the assured us it was fully safe to use, we tested it for about a week before putting any animals in it. we noticed the top of the AC unit was blowing a small amount of hot air out of the top so we let our contractor know as we were worried about it. he assured us it was fine and he just taped over it so the air would only blow out the tube (? i have no idea how this all works we trusted he knew what he was doing) everything was fine after that so we put them in.

it has been less than a month and we just woke up to all of them dead. the vent he taped on fell off and it heated from 60° to 100° in an hour while we were asleep. i’m so besides myself and have no idea what to do. is this something that can be pursued for negligence? i’m so devastated as all of this was so avoidable and we bought this specific shed and set up everything the way he told us it would be safe to do so. he promised up and down it was safe. i’ve had one of my babies for over 15 years and i can’t believe he was taken from me like this. please help thank you so much

Location: California