First Interstate BancSystem, Inc. Insider Trading Activity

Insider Trade Summary

Net Seller: 55,000 shares

Net Sell 1 txn

Insider Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees

Role 10% Owner

Sold 55,000 shs ($1.53M)

Type	Security	Shares	Price	Value
Sale	Common Stock	55,000	$27.86	$1.53M

Holdings After Transaction: Common Stock — 529,256 shares (Indirect, See Footnote)

Footnotes (3)

1. F1. Composed of 529,256 shares held of record by Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees.
2. 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.
3. F3. The price reported in column 4 is a weighted-average price. These shares were sold in multiple transactions at prices ranging form $27.60 to $28.28. The reporting person undertakes to provide to First Interstate BancSystem, Inc., any security holders of First Interstate BancSystem, Inc., or the staff of the Securities and Exchange Commission, upon request, the full information regarding the number of shares sold at each separate price within the ranges set forth above.

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Accepted by SEC EDGAR 08/01/2025 - 04:17 PM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees

(Last) (First) (Middle)

P.O. BOX 7113

(Street)

BILLINGS, MT 59116

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
FIRST INTERSTATE BANCSYSTEM INC [ FIBK ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/01/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/01/2025		S		55,000	D	$27.86(3)	529,256(1)	I	See Footnote(2)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Composed of 529,256 shares held of record by Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees.

2. 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.

3. The price reported in column 4 is a weighted-average price. These shares were sold in multiple transactions at prices ranging form $27.60 to $28.28. The reporting person undertakes to provide to First Interstate BancSystem, Inc., any security holders of First Interstate BancSystem, Inc., or the staff of the Securities and Exchange Commission, upon request, the full information regarding the number of shares sold at each separate price within the ranges set forth above.

	SUSAN SCOTT HEYNEMAN TRUST, SUSAN HEYNEMAN & FIRST INTERSTATE WEALTH MANAGEMENT CO-TRUSTEES, By: /s/ Timothy Leuthold, Attorney-in-Fact for Reporting Person	08/01/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.