On a ceiling, there were tiny droplets of blood less than 1 mm in diameter. the victim was lying in a pool of blood. no other marks were found on the other walls. which best explains the sequence of events?

the victim was shot with a gun from behind and collapsed on the floor beneath.

the victim shot himself in the mouth.

the victim was stabbed with a knife.

the victim was hit in the head with a blunt object.

"On a ceiling, there were tiny droplets of blood less than 1 mm in diameter." this can discard the knife theory.

"No other marks were found on the other walls" this is an interesting part, because usually a bullet would leave a mark in the walls or the ceiling, and this is not the case here, so we also could the "shot from behind"

"The victim was lying in a pool of blood". A hit in the head, actually could cause a hemorrhage, and maybe also could spread the tiny droplets of blood, because they have 1mm diameter, they are really tiny . But the second option is the really more likely, the only problem here is that there are no marks of a bullet in the ceiling.