See #19.Sorry I couldn't link you.
There's a difference between "not a suspect" and "not involved." The reports I've seen only say he's not a suspect, but the ATF wants to talk to him. There's also a BOLO (Be On the LookOut) for him in Maryland, with a more detailed description of the vehicle on this
thread. I'd assume the other jurisdictions (DC Police, Virginia) are also interesting in having a little chat with Mr. Baker.