Need Help with dapp testnet

I was trying to build dss-deploy-scripts from makerdao github accroding to docs but I got an error when used dapp testnet command :

Fatal: Failed to write genesis block: database contains incompatible genesis (have 36e0fd38f5fc4e17c59365b6a25c3402ed2cd4d47b634718fad38e3a7c84e65a, new 0f7291a432b22ddef4339b8016267491e4d717a4fafb15da8d26a8c61f2c0c2a)

I think it may be because I have run the testnet before and the same testnet may be up and running somewhere but how can I shut it down to start a new one? or view the already running testnet?