You can use this API exposed by etherscan.io: https://etherscan.io/apis#logs

Remember to set the right topic, as mention in this other answer: What is topics[0] in Event logs?

Given a txtid is possible to retrieve the logs of the transaction via web3 using the getTransactionReceipt() function.

Alternatively, you can use this API exposed by etherscan.io: https://etherscan.io/apis#logs

Remember to set the right topic, as mention in this other answer: What is topics[0] in Event logs?