On the one hand, Atlas felt as if his consciousness was drowning, unable to get back again; on the other hand, his body was following the urge for blood.
The entire street was covered in blood as Atlas ruthlessly killed more and more Vampires. The more he killed, the stronger he became as he was able to use the Vampire Blood as well.
The Carlisle Clan heads didn't realize that. They thought that Atlas was only drinking the Blood of Vampires because he had lost his senses as they knew that the Vampire Blood was generally useless for them. They thought it was the same for Atlas, not realizing that Atlas was different.
As a Progenitor, Atlas had the advantages that they didn't have, and one of those advantages was the ability to drink vampire blood without getting sick.