An Iowa man has been charged with two counts of first-degree murder after two policemen were shot dead on Wednesday.
Police said on Thursday that a search dog recovered a high-powered rifle from a wooded area. They believe Scott Greene fired this during the ambush-style attacks.
Greene was charged in connection with the deaths of Des Moines Sergeant Anthony Beminio and Urbandale officer Justin Martin.
Beminio, 38, and Martin, 24, were shot on Wednesday while sitting in their patrol cars in separate incidents less than two miles apart. Several bullets were fired into the vehicles.
The .223-calibre rifle believed to be used was discovered on Wednesday by a police dog apparently hidden in a wooded area "where no person probably could have found it," said Des Moines police spokesman Sergeant Paul Parizek.
Court documents have shown 46-year-old Greene was under intense financial pressure. He had been ordered to move out of his mother's basement just hours before the incident.
He left hospital on Thursday and was being questioned by detectives at the Des Moines police station.
He had been hospitalised for treatment of a pre-existing medical condition following his surrender on Wednesday morning.
The documents showed Greene, an unemployed father who lived in the Des Moines suburb of Urbandale, was increasingly desperate for money in recent weeks.
District Judge Carla Schemmel ruled on Tuesday that Greene had committed elder abuse against his 66-year-old mother Patricia Greene by "physically hitting and financially exploiting" her.
She ordered him to move out of his mother's home, where he had been living in a basement bedroom, before November 6 and to stay away from the home for a year.
Greene had applied for the restraining order on October 19, two days after she was arrested and charged with striking her son in the face during an altercation that he had recorded with his mobile phone.
She wrote in the application that she believed her son "set me up to get me in trouble".
Greene wrote that while she was in jail, her son told one of her friends that Greene needed to give him $20,000 (£16,000) and that if his mother paid, "he would move and not bother" her again.
A temporary protective order was issued on October 20.
Schemmel issued the permanent order during Tuesday's hearing, where it was served on Greene.
The order, which warned that any violations would lead to his arrest, also directed Greene to return $10,000 (£8,000) to his mother and to not take any of her assets.