DCI Finds Deputy Justified in Fatal Shooting
The Division of Criminal Investigation concluded a Minnehaha County deputy acted lawfully when firing during a Sioux Falls mental health warrant service that killed Deputy Katherine Frank.
Updated on Nov. 6, 2026 in Law Enforcement
On October 9, 2026, three Minnehaha County Sheriff's Office deputies serving a mental health detention warrant in Sioux Falls were confronted by Brandon Oetken, who fired once and hit Deputy Katherine Frank, who died October 12. The Division of Criminal Investigation found the deputy who returned fire was justified in using force.
Why it matters
The findings address whether the force used by deputies during a mental health warrant service was lawful, a question that bears directly on how local officers respond when a subject is armed. Oetken has been charged with first-degree murder and second-degree murder by the Minnehaha County State's Attorney's Office.
Brandon Oetken, 39, faces first-degree murder and second-degree murder charges filed by the Minnehaha County State's Attorney's Office. The DCI findings closing the review of the deputies' use of force do not resolve those pending criminal charges.
The players
Division of Criminal Investigation
The state agency that processed the scene, examined evidence, interviewed those involved and reviewed body camera video in this review.
Minnehaha County Sheriff's Office
The county law enforcement agency whose three deputies served the mental health detention warrant at the Sioux Falls home.
Minnehaha County State's Attorney's Office
The county prosecutor's office that charged Brandon Oetken with first-degree murder and second-degree murder.
Jackley
South Dakota Attorney General who announced the DCI review findings on November 6, 2026.
The details
Three deputies went to a Sioux Falls home to serve a mental health detention warrant on Oetken, who did not comply with verbal requests to leave the house. He pointed a firearm at the deputies and fired once, hitting Deputy Frank; a second deputy fired four times and hit Oetken, whose wound was not life-threatening.
Timeline
October 9, 2026: Shooting occurs at a Sioux Falls home during the warrant service.
October 12, 2026: Deputy Katherine Frank dies.
November 6, 2026: Attorney General Jackley announces the DCI review findings from Pierre.
Legal Context
The DCI review is one of six officer-involved shootings in South Dakota this year, a count that places this finding within a recent run of state use-of-force reviews. The outcome turns on whether the deputy's use of force met the standard the state applies to officers facing an armed subject.
Residents of Sioux Falls and Minnehaha County may see the findings shape how local deputies handle mental health warrants involving armed subjects. The outcome of the pending murder charges against Oetken will determine the next procedural step for the case in local courts.
The takeaway
Warrants serving mental health detentions can turn dangerous quickly, and the DCI review shows how state investigators assess deputy force after a fatal encounter. Readers following local public safety can track the pending charges in Minnehaha County as the case proceeds.
Further reading
Explore more Law Enforcement coverage from Sioux Falls and across the region.
