Jason Eaton went to his girlfriend's Indiana home last week with an engagement ring, he told police.
He planned to propose to Wendy Sabatini, according to court documents.
But Sabatini told Eaton "no" before he even got the question out.
Then, Eaton grabbed a gun, he later told police.
Eaton now stands accused in the fatal shooting of Sabatini. The Greensburg Daily News reports that Eaton faces a murder charge in connection with Sabatini's death, a crime authorities say he has confessed to.
Eaton walked into the Greensburg police department on October 26 and asked to speak to an officer, according to a probable cause affidavit. He told the officer that he had killed his girlfriend, and authorities went out to check on Sabatini.
They were met at Sabatini's Indiana home by her son, who thought his mother was still at work. The son was eating dinner after an internship, and was "unaware of any problems in the home," the affidavit notes.
"Officers searched the residence and found Sabatini deceased in an upstairs bedroom from an apparent single gunshot wound to the crown of her head," the documents read. "A firearm located inside the bedroom was found and seized."
After Eaton was detained at the police station, he told police about the failed proposal attempt and subsequent shooting.
"Eaton advised that earlier in the afternoon, he was speaking to Sabatini in the upstairs bedroom and approached her with an engagement ring, with the intent to ask Sabatini to marry Eaton. Sabatini declined before he asked," the court documents state. "Eaton said that he then retrieved a firearm from a nightstand and moved behind Sabatini, who was seated on the opposite side of the bed. Eaton said the gun fired, striking Sabatini in the head."
Eaton told police that he left the gun in the bedroom and went downstairs. Eventually, he told investigators, he left the house and travelled to the home of another woman.
Eaton told that woman "that he messed up and he thinks he killed Sabatini," the affidavit states. The pair then drove to the police department.
The affidavit notes that the investigation is ongoing, "with regard to intent, motive and timeline".
"The investigation by the Greensburg Police Department is ongoing," Prosecuting Attorney Nathan Harter said in a statement released to the Greensburg Daily News. "Any person charged with a crime is presumed innocent until proven guilty. This office will have no further comment on this pending criminal case, consistent with the Indiana Rules of Professional Conduct."
A message left with Eaton's lawyer was not immediately returned.
Sabatini's son, Lake, spoke with Fox 59 after the shooting, telling the station that he knew his mother, who was divorced, would turn down a proposal, saying that she simply did not want to get remarried.
"Anybody instantly would fall in love when you met her," he said of his mother. "She was a wonderful person."
Sabatini's sister told the Fox affiliate that she was shocked by Eaton's reaction to the rejection.
"I would have never seen this side out of him, but I guess you truly don't know everybody," Heather Rasmus told the station. "He just didn't get the answer he wanted."
Of her slain sister, Rasmus said: "She was a very stern woman. She stood her ground."
Sabatini's friends remembered the 44-year-old as a supportive woman who was "inspiring," according to the Logansport Pharos-Tribune. Her ex-husband recalled her smile, telling the newspaper that when they met: "I couldn't take my eyes off her."
"There was just something about her," John Sabatini told the Pharos-Tribune. "She was always smiling."