Michael Close, 24, allegedly fired a semi-automatic AK-47 rifle at Isabella Thallas, 21, and Darian Simon, 27, as they were walking their dog outside his apartment.
A court heard he opened fire after the canine pooped in a rock garden opposite his home in Devner, Colorada, US, and yelled: “Are you going to train that f***ing dog or just yell at it?”
Prosecutors played video from neighbourhood surveillance that showed Close opening his blinds and pointing the rifle at the pair as Simon bent over to pick up the pooch’s poop.
Denver police homicide investigator, Joseph Trujillo, said the shooting happened after Close and Simon argued over the dog mess outside Close’s apartment complex on the 3000 block of Fox Street at 11.40am.
Mr Trujillo told a preliminary court hearing that the ambush killed Isabella instantly and Darian was shot twice in the legs, KDVR reported.
He said authorities found six shell casings inside Close’s Ballpark neighbourhood apartment, and 18 others outside his window after the June 10 attack.
Close was charged with first-degree murder and more than a dozen other counts after he fled the scene in his car and was arrested by police later that day.
Mr Trujilllo said his girlfriend, Chelsea Thompson, told police that after the shooting her boyfriend called her crying, admitting to opening fire on two people.
Close was also crying and apologising when he was arrested, the court was told.
Thompson told police her boyfriend had recently been diagnosed with a personality disorder and battled substance abuse.
A search warrant executed inside Close’s apartment found several open containers of alcohol, cocaine residue and six shell casings, Trujillo shared. Another 18 shells were found outside the apartment window.
Police recovered an assault-style weapon, a Glock 17 and a shotgun from the home.
They also found ammunition and high capacity magazines that can hold more than 15 bullets which are banned in Colorado state.
A friend of Close reportedly told police that Close lost his job in the pandemic and struggled with being unable to go to the gym.
His defense attorney argued during cross-examination that Darian Simon was shown a photo line-up from his hospital room on June 14, pointing out the wrong suspect at the time.
Judge Teesch-Maguire still found credible evidence to hold Close, who is set for arraignment on January 4.
Close has been charged with two counts of first-degree murder, two counts of attempted first-degree murder, two counts of first-degree assault, nine counts of using a prohibited high-capacity magazine during a crime, two counts of prohibited use of a firearm, one count of disorderly conduct and four sentence enhancers for violent crime.
He was denied bond at the preliminary hearing on Monday.