I believe you get fragments for killing team mates. Please remove.
This is going to be addressed in an upcoming update.
But what about accidental TKs (like ones where you teammate accidentally walks in front of ya, or rushes a kill and your nade was there)?
Maybe only remove them if 100% of the damage was done by a teammate?
Otherwise, we'll have problems when there might be a 5v2, the team of 2 intentionally kill each other to prevent the 5 team from getting their tags.