A Snapchat image of Harry Watson.

With what appears to be a gun in his hand, the new partner of slain Geelong mother Emily Miller made a chilling social media post just hours before her death.

"You know what time it is?" he wrote.

"Time for this b---h to get cut off her s--t chat."

Harry Watson was arrested on Thursday, after his girlfriend, a mother of four children under the age of 10, was found with a gunshot wound to the abdomen at her Whittington home late on Wednesday.