[Landlord US-FL] can I keep a deposit if a tenant stole from me?

I have an efficiency I put up for rent. This is my first time doing something of the sort.

I had somebody come see it, say it was perfect and give me a deposit of $500 towards the $900 that was due to move in.

We signed a generic hand written thing that says “I received the $500 for deposit of xyz place, abc person plans to come back with remainder of the money sign lease and move in”

There was no dates or anything like that. Nothing further than what I’ve put above. I know of course looking back I need to be clearer. But this is where we’re at now.

They gave me that deposit on the 3rd, and we planned that them moving in the 15th would be fine. So verbally I agreed to take the rest of the money the 15th and let them move in then.

Now it’s the 13th and they call while I’m away. Saying they and a friend are there and wanting to see the place again, show the friend etc., I say sorry I wasn’t expecting you today so I’m not around and no way I can get there today. They say that’s okay we can come back, and mentioned that they were having trouble with their lug nuts on their truck and was getting rides from the friend basically.

Since I was not expecting them to come that day, I had an electric impact and a big bag of impact sockets (used primarily for loosening and tightening lug nuts effortlessly) sitting out in the open near the side door.

Now when I get back around the next day, (14th) I realize my tools are gone. I have left valuables outside and in the yard for weeks months even and nothing ever gets touched out here. And now that this tenant has popped up, not even moved in yet, something they admitted to needing is missing.

Part of me says give the deposit back, and just tell them you’ve decided not to rent it or something. But on the other hand, they have wasted my time since the 3rd of the month now when this could have likely been rented and occupied by now. They’ve also stolen from me which I just don’t want to deal with them as people if they’re doing that already. I have a property next door that I have valuables all over the place and am not interested in having to worry about everything. So I feel it’s a fair reason that I don’t want to rent to them and am breaking my agreement. The tools missing are probably worth about $250 if I was replacing them.

There’s also the weeks I’ve lost that it could’ve been rented.

Can I keep the deposit? Is that fair? Sorry if that’s an ethical question