DUBUQUE COUNTY, Iowa — A multi-jurisdictional traffic stop along Highway 151 near Cascade turned deadly in the early hours of July 1, 2025, leaving one suspect dead and a Dubuque County Sheriff’s Office (DCSO) sergeant injured, authorities reported.

At approximately 4:30 a.m., officers from the DCSO, Dubuque Police Department, Iowa Division of Narcotics Enforcement, Monticello Police Department, and Jones County Sheriff’s Office conducted a traffic stop on Highway 151, just north of the Highway 136 interchange. The stop was part of an ongoing multi-agency investigation, according to the Iowa Division of Criminal Investigation (DCI), which was called to assist following the incident.

During the stop, the suspect, identified as James Sherrill, 36, of Linn County, Iowa, reportedly displayed a handgun. Shots were fired, resulting in both Sherrill and DCSO Sergeant Adam Williams being struck by gunfire. Sherrill, the sole occupant of the vehicle, was pronounced dead at the scene.

Sergeant Williams, a 46-year-old, 18-year veteran of the DCSO, was transported to MercyOne Emergency Care in Dubuque before being transferred to the University of Iowa Hospitals and Clinics. He was treated for a gunshot wound and has since been released.

The other officers involved were identified as Officer Chad Leitzen, 49, a 23-year veteran of the Dubuque Police Department, and Officer Cole Millard, 42, a 2-year veteran of the Monticello Police Department.

The incident remains under investigation by the DCI, with findings to be reviewed by the Dubuque County Attorney’s Office and the Iowa Attorney General’s Office upon completion. Authorities have stated that no further details will be released at this time.

The shooting underscores the risks faced by law enforcement during high-stakes operations and has prompted an outpouring of support for Sergeant Williams’ recovery and the officers involved. The investigation is ongoing, and the community awaits further updates as the DCI works to provide clarity on the events that unfolded.

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