FLANDREAU, S.D. (AP) — South Dakota prosecutors will seek the death penalty for a Sioux Falls man charged in the death of a deputy who was struck while putting out spikes during a police chase.

The South Dakota Attorney General’s office filed an official notice Wednesday announcing it will seek the penalty for Joseph Gene Hoek, 40, in the death of Moody County Chief Deputy Ken Prorok, 51, of Wentworth, who died during the pursuit on Feb. 2.

Hoek pleaded not guilty Wednesday to charges of first-degree murder and aggravated eluding. Hoek’s attorneys said they plan to seek a mental health evaluation of their client and will consider entering a plea of insanity to the charges.

Attorney General Marty Jackley said he made the death penalty decision after reviewing the circumstances and meeting with the victim’s family and the sheriff who were at Wednesday’s hearing. Jackley said the fact that Prorok was killed in the line of duty and that it happened while Hoek was trying to evade arrest made the crime worthy of the death penalty.

When he was charged, investigators described Hoek as being on a “downward spiral” marked by drug use and escalating threats of violence.

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The pursuit started after officers responded to a call about a man, identified as Hoek, making “homicidal threats” near the business where the caller worked. Police spotted his car and tried to stop him, but Hoek sped off on Highway 34 toward Interstate 29, Special Agent Jeffrey Kollars of the South Dakota Division of Criminal Investigation wrote in a court filing.

The chase reached 115 mph (185 kph). Prorok stopped to deploy stop spikes across Highway 34. But a witness said he saw the approaching car intentionally swerve and strike the chief deputy before it went into the ditch and flipped, the agent wrote. Hoek ran off on foot. The witness followed Hoek, ran him down and detained Hoek until officers arrived.