NEVADA, Ia. — When Collin Richards was interviewed the day Celia Barquin Arozamena was found stabbed to death on an Ames, Iowa, golf course, his hand was still bleeding, authorities said.

The 22-year-old man, whom police described as homeless, told the Iowa Division of Criminal Investigation agent he'd cut his hand days before. But an examination of Richards' injury, state investigators said, was consistent with one of two serration marks found on Barquin Arozamena's body.

Barquin Arozamena, the 2018 Big 12 women's golf champion and Iowa State Female Athlete of the Year, was found dead on the morning of Sept. 17 at the Coldwater Links golf course. The civil engineering student died of multiple stab wounds, police said.

Richards has pleaded not guilty to first-degree murder. He entered the written plea of not guilty Monday in Story County District Court, online court records show. An in-person arraignment was canceled. The document was signed by Richards on Oct. 9.

More:Iowa State video details slain golfer's transition to America

In the days after Barquin Arozamena was found, authorities executed search warrants looking for knives, fingerprints and other physical evidence, according to court documents made public last week.

Barquin Arozamena's puncture wounds could have been caused by a knife with a blade at least 4 inches long, authorities said. Investigators have found three knives in an investigation into the killing, the recently released records show.

One knife was found at a campsite in Ames to which Richards has been connected.

Officers investigating Sept. 20 a garage fire at a home where police said Richards showered after the slaying found two kitchen knives, one serrated, with blades longer than 4 inches. The blaze, estimated to have caused $10,000 in damage, remains under investigation, the fire department said.

Investigators haven't said which of the knives may have been used in the slaying.

During an autopsy and subsequent forensic examination, officials determined the golfer's body had two serration marks, one of which was larger than the other.

In one of eight search warrant applications, an agent detailed Barquin Arozamena's gruesome injuries to her upper torso, head, neck and left leg.

Blood was found on the golf course fairway, the records show.

Barquin Arozamena appeared to be missing clothing when she was found in a sports bra and a golfing skirt, authorities said.

A man told agents he'd recently seen Richards carrying a large knife with a serrated back edge, which he used to cut wood, according to court records.

Ames police officers who reported previous interactions with Richards also said he had been in possession of various knives before.

An Ames police officer took Richards to the Mary Greeley Medical Center’s emergency room. Agents requested his medical records from that trip to investigate the depth of the cut on his hand and when he might have received it, records show.

An acquaintance of Richards' told police that Richards had recently stayed with him at an encampment consisting of two tents near the dead end of the 600 block of South Maple Avenue, near the north bank of Squaw Creek, across from the golf course. Police used K-9 units to trace Barquin Arozamena's scent to the camp.

There, agents have since seized six articles of clothing that police said had apparent blood stains, both tents, two blankets and a backpack.

When officers found Richards there, he had several fresh scratches on his face that were consistent with fighting, according to a criminal complaint. Police said he tried to hide the deep laceration on his hand by sitting down and sticking his hand in the dirt.

Investigators also executed search warrants for Richards' fingerprints and his Facebook account. He did not appear to have a cellphone.

The social media account, which agents suggested belonged to him, showed a publicly viewable photo updated in July that depicted a comic of a person holding a filled coffee cup with a caption "let's go commit a murder." The person was depicted adding milk to the coffee with another caption that investigators said read "let's contemplate a murder."

Investigators were waiting for information back from Facebook as of last week. Detectives requested Richards’ photographs and private messages from mid-July through the day after Barquin Arozamena was killed, records show.

When Richards arrived at the home, where authorities said he took a shower, he was disheveled and covered in blood, sand and water, a witness told police. He bathed, then left with blood-stained clothes in a black backpack, according to court records.

The search warrants showed Richards arrived at the home on a black Huffy bicycle, which he left at the residence; officers seized it to preserve trace evidence. Investigators collected swabs from the home’s bathroom.

Richards' acquaintance told police in the days before he was arrested, Richards made a statement about having “an urge to rape and kill a woman,” authorities said.

Richards has pleaded not guilty to the charge. One of Richards’ public defenders, Paul Rounds, has said he hopes the public reserves judgment about his client until the trial.

If convicted of first-degree murder, Richards faces life in prison.

The Associated Press contributed to this report.