It cant be Jane because why would he kill his own family.
I think it could be Teresa Lisbon but it might not because she is the leader and she always seems upset when she sees someone die but she might be because when she has a bad guy shes not afraid to kill them even if there is no harm in her or anyone else's way. So that is why I think that it could be someone else because all of the people on there could keep the secret of killing Jane's family and still work so close with him and be such great friends with him.
So it must be someone else