Rahasyamay Qatil

A couple Devyani and Veer are on their way to collect some money from Veer's friend, Prabhaat. His servant informs them that Prabhaat was in a bad mood and he should not be disturbed. When he comes out he can be seen irritated with his friends and tells his servant to give them their money, later Prabhaat is found dead by them. CID investigates and finds that there are no wounds on him and door and windows were completely shut. How was he murdered?