If you don't have probate counsel, you should obtain probate litigation counsel to petition the court to have that co-executor removed from the executorship of the will, and seek reimbursement to the estate, or surcharge that person's share of the estate if they are entitled to share in the estate. If you don't move expeditiously, to report this to your attorney or the court, you could be liable for the losses suffered by the estate as a result of the other co-executor conduct, because that conduct is theft from the estate and has criminal penalties.