The Vampires Had It Covered

"It's confirmed, it was done by a vampire," General Alaska reported to Romulus who was seated on the throne.

"It wouldn't have been surprising if you told me that was the work of the witches. But to think that our kind did that is kind of heartbreaking," Romulus sighed. 

His silver gaze stared at General Alaska asking, "And the body?"

"Deposited in the morgue as we speak. Although our scientist would be working on the body to be able to trace the vampire who killed her." General explained to the king. 

Just like humans had DNAs that can be traced, vampires were the same as well except that their chromosomes weren't the same as humans. And while detectives back on earth tracked the perpetrator of the crime after due investigation with their technology, vampires made use of abilities.