The records, obtained by The Associated Press, also show a vehicle wanted in a double killing in Boston a year before had been rented in Hernandez's name.
Together, the revelations provide the most damning evidence yet against the 23-year-old star athlete.
Hernandez has been charged in the June killing of Boston semi-pro athlete Odin Lloyd. The records say Hernandez associate Carlos Ortiz told Massachusetts investigators that another man, Ernest Wallace, said Hernandez shot Lloyd in an industrial park near Hernandez's home in North Attleborough.
The gun used in the killing has not been found.
The documents were filed in court by the Miramar, Fla., police department to justify a search of Wallace's mother's home in that city.
The records also show that police, while investigating Lloyd's killing, searched in Hernandez's hometown of Bristol, Conn., and found a vehicle wanted in connection with a July 2012 double homicide near a Boston nightclub.
Hernandez has pleaded not guilty in Lloyd's killing. His legal team did not return email messages Tuesday. Wallace faces an accessory to murder charge in the case and has pleaded not guilty.
Prosecutors say Hernandez, Wallace and Ortiz drove with Lloyd in a rented Nissan Altima to the industrial park where Lloyd was fatally shot.
Ortiz told police that during the drive Hernandez told Lloyd that Lloyd had been "chilling" with people Hernandez had problems with, the documents say. But Ortiz told police the two men shook hands and the problem seemed smoothed over. However, the Altima soon stopped, and everyone but Ortiz got out to urinate, according to Ortiz's account.
The witness told police he then heard gunshots before Hernandez and Wallace got back into the car without Lloyd and the car sped away.
Ortiz said he couldn't see who fired the shots because it was dark. Back at Hernandez's home, Ortiz said, Wallace asked him to get a small gun out from under the driver's seat. Ortiz said he did and gave it to Hernandez once they were inside.
Ortiz said he then went to sleep. When he woke up in the afternoon, according to his account, the three men returned the Altima and rented a Chrysler 300 before returning to Hernandez's home. Ortiz and Wallace then went to an apartment in the area that Hernandez and other football players used. Wallace let Ortiz in before leaving for a long time, the documents say. The two then drove to Bristol. Ortiz told police Wallace said Hernandez shot Lloyd.
Hernandez, Wallace and Ortiz appear linked through Bristol. Wallace told Florida police he grew up with Hernandez's father. Ortiz's attorney, John Connors, said Tuesday his client, who's athletic and around the age of Hernandez's older brother, is from Bristol.
Meanwhile, eight search warrants were unsealed in Massachusetts after news organizations sought access to them. The warrants reveal the breadth of the investigation, with authorities scouring through everything from Hernandez's house to his phone to the contents of his team locker, which the Patriots emptied into a container after they released him.
A rifle, ammunition and video surveillance equipment were among the items police seized from Hernandez's home.
Records show Hernandez, who played tight end, became "argumentative" during his first encounter with police at his home about five hours after Lloyd's body was found by a jogger. Hernandez told police he had last seen Lloyd in Boston the day before. He asked, "What's with all the questions?" and locked the door behind him.
He then returned with his attorney's business card but didn't respond when police told him they were investigating a death, the records show.
"Mr. Hernandez slammed the door and relocked it behind him," the records read. "Mr. Hernandez did not ask officers whose death was being investigated. Mr. Hernandez's demeanor did not indicate any concern for the death of any person."
Hernandez came out later and agreed to be questioned at a police station.
The documents also say Hernandez called his girlfriend's cellphone and stopped her from speaking with police after they pulled her over and told her Lloyd was dead.