Sec Form 4 Filing - HEYNEMAN JOHN M JR @ FIRST INTERSTATE BANCSYSTEM INC - 2023-06-01

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

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person HEYNEMAN JOHN M JR 2. Issuer Name and Ticker or Trading Symbol FIRST INTERSTATE BANCSYSTEM INC [ FIBK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) P.O. BOX 7113 3. Date of Earliest Transaction (MM/DD/YY) 06/01/2023 (Street) BILLINGS, MT59103 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 Class A Common Stock 06/01/2023 A 3,401 ( 1 ) A $ 0 24,531 D Class A Common Stock 1,402,432 ( 2 ) I see footnote ( 3 ) ( 4 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other HEYNEMAN JOHN M JR P.O. BOX 7113 BILLINGS, MT59103 X X John M Heyneman Jr. Trust P.O. BOX 7113 BILLINGS, MT59103 X Rae Ann Morss & John Heyneman Jr., Trustees FBO Rae Ann Morss Exemption Trust Under the Scott Family 1996 Trust P.O. BOX 7113 BILLINGS, MT59103 X Riki Rae Scott Davidson & John Heyneman Jr., Trustees FBO Riki Scott Davidson Exemption Trust Under the Scott Family 1996 Trust P.O. BOX 7113 BILLINGS, MT59103 X Towanda Investments Limited Partnership P.O. BOX 7113 BILLINGS, MT59103 X Signatures JOHN M HEYNEMAN JR. TRUST, By** 06/05/2023 Signature of Reporting Person Date JOHN M. HEYNEMAN, JR., By:** 06/05/2023 Signature of Reporting Person Date TOWANDA INVESTMENTS LIMITED PARTNERSHIP, By:** 06/05/2023 Signature of Reporting Person Date RAE ANN MORSS & JOHN HEYNEMAN JR., TRUSTEES FBO RAE ANN MORSS EXEMPTION TRUST UNDER THE SCOTT FAMILY 1996 TRUST, By:** 06/05/2023 Signature of Reporting Person Date RIKI RAE SCOTT DAVIDSON & JOHN HEYNEMAN JR., TRUSTEES FBO RIKI SCOTT DAVIDSON EXEMPTION TRUST UNDER THE SCOTT FAMILY1996 TRUST, By:** 06/05/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares issuable upon vesting of restricted stock units granted to the reporting person pursuant to the Registrant's 2023 Equity and Incentive Plan. The restricted stock units vest on June 1, 2024, subject to the reporting persons provision of continuous service to the Registrant through the vesting date. ( 2 )The reporting person no longer has a reportable beneficial interest in 890 shares of FIBK common stock owned by his son and included in the reporting person's prior ownership reports. ( 3 )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 and 5, if any, together with John Heyneman, Jr. with the indication of direct or indirect ownership in Table I being made from John Heyneman, Jr.'s perspective. The nature of beneficial ownership is described in detail by footnote for all reporting persons. ( 4 )Composed of 139,921 shares held of record by John M Heyneman Jr. Trust, 85,836 shares held of record by Riki Rae Scott Davidson & John Heyneman Jr., Trustees FBO Riki Scott Davidson Exemption Trust Under the Scott Family 1996 Trust, 85,836 shares held of record by Rae Ann Morss & John Heyneman Jr., Trustees FBO Rae Ann Morss Exemption Trust Under the Scott Family 1996 Trust, 1,085,792 shares held of record by Towanda Investments Limited Partnership, 3,977 shares held of record by John Heyneman, Jr.'s spouse, 890 shares held of record by John Heyneman, Jr.'s son, and 1070 shares held of record by John Heyneman, Jr.'s daughter.

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).

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