The will or intestacy order, probate grant, the executor's final accounting and the transfer records, plus enough of your father's history to show lawful accumulation: property titles, employment or business records and several years of tax returns. Ask the executor before the estate closes.
Get the estate file while the executor still has it
The investor's own link to the money is proven by the probate documents and the distribution: the will naming her, the court's grant, the executor's accounting listing the assets, the debts paid and the amount distributed, and the bank record of the deposit into her account. The deceased's link to the money is the part families underestimate. If the estate was largely a house and a pension, the property title history, the mortgage discharge and the pension statements cover it.
If it included a business, the business's financial statements and sale documents are needed. Several years of the parent's tax returns, obtained through the executor from the Canada Revenue Agency, show declared income consistent with the assets. Statements for the accounts the estate was paid from complete the path.
All of this is easiest to obtain before the estate is wound up and the executor's authority ends, so the request should go in immediately, even if the EB-5 decision is months away.