SIOUX CITY — As he stabbed his ex-girlfriend numerous times, Tran Walker told police, he "wanted her to feel the pain he was feeling" since she had broken up with him, according to information contained in court documents filed Monday.

Tran was upset that Paiten Sullivan would not continue their relationship and began stabbing her early Sunday while they were riding in a vehicle with a mutual friend, Felipe Negron Jr., who was fatally stabbed as he tried to intervene, according to a complaint and affidavit filed in Woodbury County District Court.

Tran, 18, of Sioux City, is being held in the Woodbury County Jail on two counts of first-degree murder. District Associate Judge Todd Hensley set bond at $1 million at Tran's initial appearance early Monday morning. A preliminary hearing was set for Feb. 8.

According to court documents, Tran, Sullivan and Negron were in a Chrysler PT Cruiser at about 1:19 a.m. Sunday at Jay Avenue and South Cecelia Street when Tran became upset and began stabbing Sullivan, then Negron. The Sioux City Police Department responded to the area soon after receiving a report that two people had been stabbed multiple times.

Negron, 18, and Sullivan, 17, both of Sioux City, were transported to Mercy Medical Center-Sioux City, where they were pronounced dead. Police have not formally identified Sullivan as a victim, though several of her friends have confirmed her death on social media.

Autopsies were to be performed Monday at the Iowa State Medical Examiner's office in Ankeny, Sioux City Police Sgt. Ryan Bertrand said.

Walker was found shortly after 2 a.m. Sunday at the Hy-Vee store on Gordon Drive after several bystanders reported there was an injured man at the store. Officers reporting to the scene determined that he fit the description of the stabbing suspect and took him into custody. He was treated at UnityPoint Health-St. Luke’s for injuries consistent with knife wounds on his hand.

Bertrand said Walker was in possession of a knife when he was arrested, but it was not believed to be the weapon used in the stabbings. Police later took possession of the knife they believe Walker used to stab the victims.

"We recovered the weapon used," Bertrand said.

Police believe Negron was driving the vehicle when Walker began stabbing Sullivan.

"The three people involved — the two victims and the suspect — were originally in a vehicle and had been riding around together. We believe the assault was initiated/started in the vehicle and after the vehicle came to a stop it continued," Bertrand said at a Sunday news conference.

Some civilians came to the victims' aid shortly after the assault, and Negron, who was still conscious at the time, was able to provide them with some information, Bertrand said.

During his interview with police after his arrest, Walker admitted stabbing Sullivan multiple times because he was upset that she had broken up with him and he wanted her to feel his pain, court documents said. Walker also admitted stabbing Negron after he tried to stop him from stabbing Sullivan, court documents said.

The investigation is ongoing, Bertrand said Monday.

Court documents gave no other details of the incident, saying only that Walker acted with "malice aforethought, willfully, deliberately and with premeditation to kill (his victims)," all legal elements of the charge of first-degree murder.

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