[Form 4] FIRST INTERSTATE BANCSYSTEM INC Insider Trading Activity

Rhea-AI Filing Summary

Susan Scott Heyneman Trust and co-trustees reported multiple disposals of First Interstate Bancsystem, Inc. (FIBK) common stock between 09/09/2025 and 10/01/2025. The filings show sequential dispositions of 152,160, 45,154, 67,482, and 10,000 shares, for total reported sales of 274,796 shares. After these transactions the reporting parties state they hold 244,460 shares of record via the Susan Scott Heyneman Trust.

The Form 4 notes the reporting persons may be part of a group with other signatories and disclaim beneficial ownership except to the extent of pecuniary interest. The Form is signed by an attorney-in-fact on behalf of the trust on 10/03/2025. The filing discloses quantities and sale price for the 10,000-share sale at $31.59; earlier dispositions are coded as voluntary/other and reported with $0 price entries reflecting non-open-market transfers or internal adjustments per reporting conventions.

Positive

• Timely disclosure of multiple transactions via Form 4, signed on 10/03/2025
• Final recorded holdings clearly stated as 244,460 shares held of record by the trust

Negative

• Substantial net disposals totaling 274,796 shares between 09/09/2025 and 10/01/2025
• Group beneficial ownership disclosure may indicate shared reporting with other signatories, complicating sole-ownership clarity

Insights

Insider Transactions Analyst

TL;DR: Reporting parties sold 274,796 FIBK shares; record holdings now 244,460.

The Form 4 discloses four dispositions between 09/09/2025 and 10/01/2025, with an explicit cash sale of 10,000 shares at $31.59. The other three entries show $0 prices and are coded differently (W), indicating non-ordinary-market transactions or transfers as reported.

The filing also states the reporting persons "may be deemed" members of a group sharing beneficial ownership; however, they disclaim ownership except for pecuniary interest. This group disclosure affects how the aggregate holding is viewed but contains no additional numeric detail beyond the stated 244,460 shares held of record.

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

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

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)
09/09/2025

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	09/09/2025		W		152,160	D	$0	367,096	I	See Footnote(2)
Common Stock	09/10/2025		W		45,154	D	$0	321,942	I	See Footnote(2)
Common Stock	09/17/2025		W		67,482	D	$0	254,460	I	See Footnote(2)
Common Stock	10/01/2025		S		10,000	D	$31.59	244,460(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 244,460 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.

	SUSAN SCOTT HEYNEMAN TRUST, SUSAN HEYNEMAN & FIRST INTERSTATE WEALTH MANAGEMENT CO-TRUSTEES, By: /s/ Timothy Leuthold, Attomey-in-Fact for Reporting Person	10/03/2025
	** 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.
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FAQ

What insider transactions did FIBK (First Interstate Bancsystem) report?

The filing reports four dispositions: 152,160 shares on 09/09/2025, 45,154 on 09/10/2025, 67,482 on 09/17/2025, and a sale of 10,000 shares at $31.59 on 10/01/2025.

How many FIBK shares does the Susan Scott Heyneman Trust report holding after these transactions?

The Form 4 states the reporting parties hold 244,460 shares of record following the reported transactions.

Do the reporting persons claim sole beneficial ownership of the reported FIBK shares?

No. The filing includes a footnote that the reporting persons "may be deemed" members of a group with other signatories and disclaim beneficial ownership except to the extent of pecuniary interest.

When was the Form 4 signed and filed for these FIBK transactions?

The Form 4 is signed by an attorney-in-fact for the reporting persons on 10/03/2025.

What price was disclosed for the 10/01/2025 transaction?

The 10,000-share sale on 10/01/2025 is reported at a price of $31.59.