All 4 bodies discovered inside a Florida mansion owned by former tennis great James Blake contained bullet wounds ... and a gun was found at the scene ... this according to law enforcement officials.
Detectives are not yet calling it a murder-suicide ... but it sure seems that way -- with new evidence showing the killer was most likely the father of the family of 4 that had been living in the Tampa home.
Officials say the gun recovered at the house belonged to Darrin Campbell -- and now video has surfaced showing Darrin buying large amounts of fireworks last Sunday.
Darrin had reportedly been out of work for the past year.
Officials say they are not pursuing any suspects in the case.