I've been seeing this more and more as of late -- it definitely appears to be either a hack or a glitch. It involves players achieving assault killstreaks that they have not earned. No care packages involved, mind you.
For instance, someone going 9-20 calling in a Maniac Juggernaut -- when he just died twice a few seconds prior in the kill feed.
I made a video demonstrating my findings. Last night we ran into at least two of these glitchers/hackers. Has anyone else ran into this yet? It seems to be getting more and more common and will require a patch to fix!