Tell your unhappy tenant that he can break the lease but he can not be refunded the month of april. Do not allow foot dragging. His is an old story. He has found another place better or cheaper and wants out of your contract.
Jake is right, they found another place... I had a similar thing with tenants. Went through the lease no lawn care -- they signed. They knew it, we spoke about it again outside. I sent an e-mail with mames of some lawn care people for them to contact and use until they bought a lawn mower. Then an e-mail came back saying that wasn't part of the lease and every house they've rented had lawn care, they were going to take us to the housing bureau or where ever and (basically get us in trouble). Bottom line, I was thrilled to be rid of them -- but I'm sure they'd found something cheaper or closer to work. Whatever it was, I was just happy to not have to deal with them.