A teenager was charged Thursday in the slayings of a man and a 7-month-old boy who were gunned down as they sat in the back of a parked car in the Midtown Phillips neighborhood last weekend.

Jquan LeeArthur McInnis, 17, of Minneapolis, faces two counts each of first-degree murder and murder in a drive-by shooting, after he shot at Gustav "Gutt" Christianson, apparently over a debt, prosecutors said Thursday. A grand jury will be impaneled in the next two weeks to confirm the charges, according to authorities.

Hennepin County Attorney Mike Freeman, reading from a statement at an afternoon news conference, said the shooting came as a surprise to those who knew McInnis, who had no history of "violence with a weapon." But, he said, prosecutors had sought to try McInnis as an adult because of the seriousness of the crime, which he called "inexplicable."

"It's not a juvenile act when you shoot somebody in broad daylight," he said. "That's homicide; that's idiocy."

Freeman refuted speculation that the shooting resulted from a gang beef, saying that it instead appeared McInnis targeted the other man because of a dispute over money. He told reporters that his office will seek the maximum sentence of life in prison against McInnis. If convicted, McInnis would be eligible for parole after 30 years, he said.

Witnesses described the suspect as wearing a blue sweatshirt and fleeing the scene near the corner of 26th Street and 11th Avenue on foot, disappearing down an alley, the complaint said. Officers later found the sweatshirt in a garage a block away from where the shooting occurred.

McInnis was arrested sometime overnight on Tuesday. It was unclear whether police recovered the gun allegedly used in the crime.

According to a criminal complaint, McInnis was driving in the area that day when he spotted Christianson, sitting in the back seat of a red, four-door sedan parked in a driveway. Prosecutors said McInnis circled the block once before getting out of the car and opening fire at the car with Christianson inside. Prosecutors said McInnis then walked around the back of the car and fired again inside, shattering the rear window.

He later told detectives that he hadn't known that the baby was in the car, said the complaint, filed Thursday in Hennepin County District Court.

Christianson was struck by multiple bullets and crawled out of the car onto the pavement, where he collapsed, authorities said. He was pronounced dead at the scene.

The infant, Jayden Redden, who was strapped into a car seat, was hit in the chest, according to authorities. Redden's father hoisted the car seat out of the car with his son in it, and drove to nearby Children's Hospital, the complaint said, but the baby later died.

Police attributed the arrest to the dogged police work and the willingness of witnesses to come forward and cooperate with the investigation.

McInnis, who is expected to be assigned a public defender at his initial court appearance Friday afternoon, was out on supervised release after pleading guilty last month in an attempted robbery case.

Libor Jany • 612-673-4064 Twitter:@StribJany