Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees - 01 Dec 2025 Form 4 Insider Report for FIRST INTERSTATE BANCSYSTEM INC (FIBK)

Role: 10%+ Owner
Signature: SUSAN SCOTT HEYNEMAN TRUST, SUSAN HEYNEMAN & FIRST INTERSTATE WEALTH MANAGEMENT CO-TRUSTEES, By: /s/ Timothy Leuthold, Attorney-in-Fact for Reporting Person
Issuer symbol: FIBK
Transactions as of: 01 Dec 2025
Transactions value $: -$327,500
Form type: 4
Filing time: 01 Dec 2025, 12:58:26 UTC
Previous filing: 03 Nov 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees	10%+ Owner	P.O. BOX 7113, BILLINGS,	SUSAN SCOTT HEYNEMAN TRUST, SUSAN HEYNEMAN & FIRST INTERSTATE WEALTH MANAGEMENT CO-TRUSTEES, By: /s/ Timothy Leuthold, Attorney-in-Fact for Reporting Person	01 Dec 2025	0001908880

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	FIBK	Common Stock	Sale	-$328K	-10K	-4.27%	$32.75	224K	01 Dec 2025	See Footnote	F1, F2

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Composed of 224,460 shares held of record by Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees.
F2	As a result of certain agreements entered into by and among the reporting persons, the Issuer, and certain other stockholders of the Issuer, the reporting persons may be deemed members of a group with the other signatories thereto and may be deemed to share beneficial ownership of the securities reported herein. Each of the reporting persons disclaims beneficial ownership of any such securities, except to the extent of its pecuniary interest therein. The reporting persons expect to file future Forms 4, if any, together with Susan Scott Heyneman, Trust.

Content

Composed of 224,460 shares held of record by Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees.

As a result of certain agreements entered into by and among the reporting persons, the Issuer, and certain other stockholders of the Issuer, the reporting persons may be deemed members of a group with the other signatories thereto and may be deemed to share beneficial ownership of the securities reported herein. Each of the reporting persons disclaims beneficial ownership of any such securities, except to the extent of its pecuniary interest therein. The reporting persons expect to file future Forms 4, if any, together with Susan Scott Heyneman, Trust.