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DENVER (KDVR) — The Denver District Attorney’s Office says Michael Close, the man accused of killing 21-year-old Isabella Thallas on June 10, 2020, pleaded not guilty by reason of insanity on Monday.

Close is accused of firing at least 24 shots from a high-powered semi-automatic rifle, killing Thallas and injuring her 27-year old boyfriend, Darian Simon, who was shot twice in his legs but survived.

Simon and Thallas were walking their dog around 11:40 a.m. when Close opened his window and allegedly yelled, “Are you going to train that f—ing dog or just yell at it?”

Isabella Thallas. Credit: Thallas family

FOX31 confirmed the gun used in the murder had belonged to a Denver officer.

Close has been charged with two counts of murder in the first degree, two counts of criminal attempt to commit murder in the first degree, two counts of assault in the first degree, six counts of using a prohibited large-capacity magazine during the commission of a crime, three counts of possessing a prohibited large-capacity magazine, one count of disorderly conduct and four counts of the sentence enhancing charge of crime of violence.