From that same Malaysian Insider article:
The source also revealed that investigators have confirmed that MH370's pilot, Captain Zaharie Ahmad Shah, was the last person to speak to air traffic controllers with the words "Good night Malaysian three-seven-zero".
According to CNN, the Malaysian source told them that there was nothing unusual about the voice and there was no indication of stress. Confirmation of the voice belonging to Zaharie came after police played the recording to five other Malaysia Airlines pilots who knew the pilot and co-pilot, first Officer Fariq Abdul Hamid.
RMAF deployed search aircraft on March 8, but did not inform anyone - The Malaysian Insider