Baton Rouge police and deputy U.S. marshals on Monday arrested three more people in the April 15, 2012, fatal shooting and apparent robbery of Brandon Harris on Sharlo Avenue in Tigerland, bringing the number of suspects to four.

Tressie Newberry, 40, 8983 Jefferson Highway, Baton Rouge; Jennifer Prine, 27, 83618 Cane Market Road, Watson; and Cameron Reynaud, 23, 4854 St. Louis St., Zachary, were booked into East Baton Rouge Parish Prison on counts of first-degree murder.

Newberry and Prine are accused of assisting Newberry’s son, Mason Chiapuzio, 19, in the slaying, police Cpl. Tommy Stubbs said.

Booking records show Reynaud was arrested later Monday in the slaying.

East Baton Rouge Parish District Attorney Hillar Moore III said Monday that his office is still filing paperwork to have Chiapuzio extradited from Michigan to Baton Rouge.

Police Cpl. L’Jean McKneely has said deputy U.S. marshals arrested Chiapuzio on Friday near Ontonagon, Mich., after authorities in that state called Baton Rouge police.

Police have said Chiapuzio will be booked into Parish Prison on a first-degree murder count upon extradition.

Authorities found Chiapuzio in Ironwood Township, about 70 miles southwest of Ontonagon, where he is being held, after Michigan State Police and Ironwood Public Safety Department and Ontonagon County Sheriff’s Department officials helped U.S. marshals arrest him, according to a news release.

Robbery appears to be a motive in the shooting because Harris’ pockets had been emptied, McKneely has said.

According to arrest warrants, a witness told police he heard gunshots and saw Harris on the ground when he walked outside. The witness said he saw a man with a shotgun go through Harris’ pockets.

Detectives learned that Harris was in contact with Newberry and Prine via cellphone throughout the last five hours before his death, the warrants indicate.

According to the warrants, Newberry and Prine, in initial interviews, denied knowing Harris, but on March 7, a confidential informant told detectives that Chiapuzio told him the day after the homicide that he shot a man on Sharlo Avenue.

The informant told police that Chiapuzio said Newberry, Prine and Reynaud were involved in Harris’ death, the warrant says.

Paula Murray, Harris’ mother, said Sunday that she first heard of Chiapuzio’s arrest from her sister, who called her Saturday at the beauty salon she owns.

Murray said she initially was upset that detectives did not call her about the arrest and that she had to learn from someone else.

But Murray said she quickly got over it and that her focus has shifted from learning the killer’s identity to finding out why the shooting happened.

“I know it’s not going to bring my son back, but I want to know why,” Murray said.

Murray said her son, known to some as “Fresh,” told her he was at a party on West Johnson Street, near the West Buchanan Street house where the family grew up, when he left with two women and a friend Murray knows as “Twin.” The four drove toward Tigerland, she said.

Murray said somebody at the party told her that her son kept looking at his phone and answering it, saying, “I’m coming.”

“It was a setup,” Murray said.

Murray said that when she finally saw her son, he was lying facedown with his pockets emptied.

“You could tell my son was running for his life because they shot him in the back, then stood over him and shot him in the head,” Murray said.

Advocate staff writers Ryan Broussard and Steven Ward contributed to this report.