McHenry County deputy found justified in fatal shootout, but report says he had chemicals sometimes used for huffing in his blood

A McHenry County sheriff’s deputy was justified in fatally shooting a man who was shooting at him, prosecutors found, though the deputy had evidence of chemicals that sometimes are used for huffing in his blood.

The shooting on Jan. 11 in Port Barrington killed Nicholas Sebastian, who had shot his wife, was threatening his children and fired multiple shots toward Deputy Nicholas Arnold, prosecutors stated in a report on their investigation.

Just after 1 a.m., Arnold and Deputy Travis Bodway responded to a domestic violence report in the 200 block of Manchester Lane in the far northwest suburb, the report stated.

When they arrived, Arnold approached the front door, the garage door opened, and Sebastian shot his wife in the leg as she tried to run out of the garage, the investigation found. Sebastian emerged, wearing a bulletproof vest and firing his gun at Arnold. Arnold emptied his gun’s magazine at Sebastian, killing him.

Two children were home at the time. In text messages with his wife before the shooting, the 43-year-old Sebastian had threatened to kill the entire family.

Testing of Sebastian’s blood revealed a blood alcohol concentration of 0.18 grams per deciliter, more than twice the legal limit for driving, plus cocaine, opioids and benzodiazepines, the report stated.

The investigation into the shooting was conducted by the McHenry County Major Investigation Assistance Team, a team of investigators from several law enforcement agencies. Upon completion of that investigation, the McHenry County state’s attorney’s office reviewed the evidence and determined that the shooting was a justified use of deadly force.

Both deputies refused to be interviewed as part of the investigation. Neither was wearing body cameras during the shooting, but a police car dashboard camera showed the shooting in poor quality.

From a blood draw following the shooting, Deputy Arnold was found to have 1,1-difluoroethane (DFE).

DFE is a gas used as a propellant in consumer products like keyboard cleaners and refrigerants. It can also be inhaled for a high, and may be detected in blood for up to 18 hours, the report stated. Side effects include cough, runny nose and congestion.

Forensic toxicologists at both Northeastern Illinois Regional Crime Laboratory and NMS Labs told investigators that the amount of DFE in Arnold’s blood was most consistent with intentional use, though police and other witnesses said there were no signs that Arnold was intoxicated at the time of the shooting.

“We are gravely concerned that Deputy Arnold may have used an intoxicant prior to his shift or while on duty,” the report concluded. “This matter is subject to an ongoing investigation.”