The man who crashed and killed an on-duty Golden Police Department officer last year pleaded guilty to various charges Monday.

Stephen Geer, 43, who was out on a $250,000 bond, pleaded guilty to one count of vehicular homicide and one count of vehicular assault in connection to the Nov. 6 crash that left 33-year-old Ofc. Evan Dunn dead, according to a news release from the First Judicial District Attorney’s Office.

Dunn’s death was the first on-duty death of an officer in the history of the department.

The plea agreement dropped one felony and two misdemeanors of the five counts he was initially charged with. Geer is required to serve four to 18 years in prison, eliminating the possibility of probation. Geer could have received probation if he had taken the case to trial.

“This stipulation reflects the parties’ acknowledgment that a prison sentence is the only appropriate outcome in this case,” the district attorney’s office said.

Geer, a former Colorado School of Mines mechanical engineering professor,  allegedly crashed into a vehicle parked at another crash on Highway 58 around 5 p.m., pushing the parked vehicle into two officers and killing Dunn.

Dunn and another officer, Bethany Grusing, were pinned under the vehicle during the crash.

Dunn died on impact and Grusing sustained a cheekbone injury. The two drivers who were involved in the earlier crash were also injured. Both were thrown by the impact and one sustained a skull fracture and brain bleed, according to arrest documents.

Grusing has since returned to work with the department. 

Geer refused a blood and breathalyzer test at the scene, prosecutor Alexa Visscher said at a previous hearing, but Geer’s blood alcohol concentration came back at a .168 at the hospital, according to prosecutor Brian Domingues at another hearing.

At the previous arraignment, Geer’s lawyer, Megan Downing, said she had just received the plea deal offer from the district attorney’s office and was still taking time to discuss it with the victims. Downing also claimed Geer was planning on coming to a resolution without a jury trial.

That resolution came Monday.

Geer is scheduled for sentencing on Jan. 21.