---
schema_version: "secwatch.filing_event.v1"
accession: "0001628280-25-029661"
form_type: "8-K"
ticker: "TUSK"
cik: "0001679268"
company_name: "MAMMOTH ENERGY SERVICES, INC."
filed_at: "2025-06-05T23:59:59+00:00"
generated_at: "2026-05-19T22:09:55.856345+00:00"
event_type: "leadership"
sentiment: "neutral"
materiality_score: 0.7
calibrated_materiality_score: 0.7
confidence: "high"
source: SEC EDGAR
---

# Mammoth Energy CEO Phil Lancaster resigns; son Bernard named COO; board changes

## Summary
- CEO Phil Lancaster resigns effective June 30, 2025; will become non-voting board observer June 11.
- Bernard Lancaster, son of Phil, appointed COO and Principal Executive Officer effective July 1, 2025.
- Paul Jacobi appointed Chief Business Officer effective July 1; resigns from board committees, loses independent status.
- Arthur Smith to retire from board at June 11 annual meeting; Mark Plaumann appointed audit committee chair and director.

## SEC filing metadata
- accession: 0001628280-25-029661
- form_type: 8-K
- ticker: TUSK
- cik: 0001679268
- company_name: MAMMOTH ENERGY SERVICES, INC.
- filed_at: 2025-06-05T23:59:59+00:00
- event_type: leadership
- sentiment: neutral
- materiality_score: 0.7
- calibrated_materiality_score: 0.7
- confidence: high
- sec_items: 5.02
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/0001628280-25-029661-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/tusk-20250530.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001628280-25-029661
- JSON: https://secwatch.observer/filing/0001628280-25-029661.json
- Plain text: https://secwatch.observer/filing/0001628280-25-029661.txt

## Key facts
- Executive change
  Paul Jacobi was appointed as Chief Business Officer at MAMMOTH ENERGY SERVICES, INC..
  - Action: appointed
  - Role: Chief Business Officer
  source text: the Board named Paul Jacobi as the Company's Chief Business Officer effective July 1, 2025.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/0001628280-25-029661-index.htm
- Executive change
  Bernard Lancaster was appointed as Chief Operating Officer and Principal Executive Officer at MAMMOTH ENERGY SERVICES, INC..
  - Action: appointed
  - Role: Chief Operating Officer and Principal Executive Officer
  source text: the Board named Bernard Lancaster as Chief Operating Officer and Principal Executive Officer of the Company effective July 1, 2025.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/0001628280-25-029661-index.htm
- Executive change
  Arthur Smith departed as Director at MAMMOTH ENERGY SERVICES, INC..
  - Action: will not stand for re-election, will retire
  - Role: Director
  source text: Arthur Smith, who has served as a director of the Company since the Company's initial public offering, will not stand for re-election at the Company's 2025 Annual Meeting of Stockholders on June 11, 2025 (the "2025 Annual Meeting"), and will retire as a director, chairman of the audit committee and member of the compensation committee and nominating and corporate governance committee, effective as of the date of the 2025 Annual Meeting.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/0001628280-25-029661-index.htm
- Executive change
  Phil Lancaster resigned as Chief Executive Officer at MAMMOTH ENERGY SERVICES, INC..
  - Action: resigned
  - Role: Chief Executive Officer
  source text: Mr. P. Lancaster has resigned from his CEO with Mammoth effective as of June 30, 2025.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1679268/000162828025029661/0001628280-25-029661-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.