His overconfidence got back at him

Alexander received the news about Stella being saved from the so called Shane's residence.

He didn't understand why he should get involved with her, so he asked them to release her and let her go wherever she wants.

If she still wanted to go to Shane, then so be it. He wasn't really interested in her choice. If not for Diana; he wouldn't even mentioned her name with his lips.

The news of Shane's residents being attacked was already in the news, same as Alex's.

After Alex discovered that it wasn't the agents that attacked Shane's resident and also learned of the blood scene before Stella's rescue; he wondered who it could be.

His mind drifted to Diana, but he quickly shook it off, but after they told him Stella's state and asked him what they should do, since they can't ask someone who doesn't look normal to leave.