Court Filings Expose 'Operation Puppet Master': HSI Infiltrated Minnesota Unions, Churches, and Activist Groups After Alex Pretti Killing

Federal court filings in the District of Minnesota — unsealed August 13, 2026 on a discovery motion by defense attorney Kevin Riach in United States v. Sant et al., Case 0:26-cr-00115 (D. Minn.), and reported the same day across KSTP, the Minnesota Reformer, AP, and CBS — revealed “Operation Puppet Master” — a Homeland Security Investigations surveillance program opened four days after federal immigration agents shot and killed Alex Pretti, a nurse and protester, in Minneapolis. Undercover HSI agents posing as protesters and activists surveilled community meetings at churches, parks, libraries, union halls, schools, and restaurants. Agents secretly recorded political discussions, entered encrypted Signal chats, collected license plate numbers, and compiled dossiers containing names, photographs, home addresses, and employment and family information. Targets included labor unions, community groups, the Sunrise Movement, and a bicycle repair collective. The Intercept reported that at least one undercover agent attempted to entice Minneapolis activists toward more confrontational tactics.

A second operation is part of this story and is often omitted. Roughly two weeks after Puppet Master, HSI opened Project Whipple Shield, named for the Bishop Henry Whipple Federal Building. Where Puppet Master targeted the activist network, Whipple Shield targeted its funding and the organizations supporting the accused — taking years of SEIU financial records, CWA donation and PAC spending statements, and PayPal and Venmo transactions for Voices for Racial Justice, all by warrantless administrative summons. An HSI slide titled “The Conspiracy,” shown to the grand jury that returned a 94-page indictment, placed 18 unions and community groups inside an “antifa network” as “council members” on the basis of alleged overlapping membership. See 2026-02-15–project-whipple-shield-hsi-financial-surveillance-minnesota-unions.

The investigation also reached outside Minnesota: HSI Saint Paul tasked HSI Detroit Metro Airport to insert an undercover agent into a church sanctuary in Ann Arbor on two days’ notice — see 2026-04-08–hsi-undercover-operation-zion-lutheran-church-ann-arbor, whose Report of Investigation names the reporting agent and the approving Resident Agent in Charge.

The predicate matters as much as the surveillance. Emptywheel’s reporting traced the investigative chain: Attorney General Pam Bondi’s high-profile “trophy arrests” of anti-ICE activists — announced with staged photos that defense attorneys argued violated a sealing order DOJ itself had requested — supplied the conspiracy predicate for the Minnesota 15 indictment and, through it, for the broader infiltration. Prosecution operated as a surveillance-expansion wedge: charge a handful publicly, then use the resulting investigative authorities to map an entire political community. At least eight prosecutions brought under the same directive in Minnesota have been voluntarily dismissed. The fifteen defendants in this case have all pleaded not guilty and their prosecutions remain live — the dismissals are of adjacent cases, not of this indictment. This is the same machinery documented when anti-ICE protesters were charged as antifa (2026-07-30–mother-jones-anti-ice-protesters-charged-as-antifa), when Prairieland defendants drew 30-to-100-year terrorism sentences (2026-06-23–prairieland-defendants-sentenced-30-100-years-antifa-terrorism), and when a federal terrorism probe was opened against Minnesota protesters banging pots and pans outside hotels housing ICE agents. Minnesota was already a designated enforcement theater — Operation Metro Surge, the Bovino criminal investigation (2026-03-03–bovino-criminal-investigation-minnesota-ice), and Bondi’s linkage of voter-roll demands to ICE enforcement (2026-01-26–bondi-voter-rolls-request-minnesota-ice-enforcement) all preceded it. The state killing of a protester did not trigger an investigation of the killing; it triggered an investigation of the people who objected.