Felony murder is charged when there are multiple suspects and police can't prove who did what. Here we only have one suspect (at least so far). I fail to see why felony murder would come into any consideration.
As Police Chief Cathy Lanier stated at the press conference, the arrest warrant IS for felony murder.
I can't remember what the aggravators she cited were, but I believe it was either because 1) he was armed, or 2) he committed kidnapping in the course of a murder.
ETA "A first-degree felony murder warrant has been issued for his arrest."
http://www.cbsnews.com/news/suspect-in-d-c-familys-brutal-murder-may-be-in-new-york-city/