Hernandez is already charged with murder in the shooting death of his friend Odin Lloyd, whose body was found June 17 near Hernandez's home in North Attleborough, Mass.
The request from Boston police in the July 2012 double homicide was based on evidence developed through the investigation of Lloyd's slaying, Bristol Police Lt. Kevin Morrell said. He said police were asked to search the same home in Bristol for both investigations, and a vehicle was seized at the address on Friday.
Two people were killed in the shooting in Boston's south end on July 15, 2012. Witnesses reported seeing people inside a grey SUV with Rhode Island plates open fire on a vehicle carrying the victims, 29-year-old Daniel Jorge Correia de Abreu and 28-year-old Safiro Teixeira Furtado.
Boston police have declined to comment on whether Hernandez is being looked as a possible suspect in that case.
Prosecutors say Hernandez, 23, orchestrated Lloyd's execution-style slaying. They say it happened after the two went to a night club a few days earlier and Lloyd spoke to people Hernandez didn't want him talking to. Two other men are also facing charges in connection with the death of Lloyd, who played linebacker for the Boston Bandits semi-pro football team. Hernandez and Lloyd were dating sisters.
Hernandez has pleaded not guilty to murder and gun charges and is being held without bail at the county jail in Dartmouth, where Sheriff Thomas Hodgson said he is acclimating well and being held alone in a cell. He gets an hour of outdoor recreation a day, an hour to shower and make phone calls, and an hour to talk to visitors per day.
Also Tuesday, a Massachusetts prosecutor asked for the public's help in finding a car mirror connected to the murder case against Hernandez.
Police are seeking the driver's side rearview mirror from a silver Nissan Altima that Bristol District Attorney Samuel Sutter said may be anywhere between Odin Lloyd's home in Boston and Hernandez's home in North Attleborough. There is about 30 miles between the locations, largely along Interstate 95, although Sutter said the mirror may be in a wooded or secluded area along the route.
Hernandez was moved to a new cell on Monday and does not have any one-on-one interaction with other inmates, Hodgson said.
The jail's Gang Intelligence Unit has completed its initial assessment, which included an inspection of multiple tattoos on Hernandez's arms and torso, for signs of past or current gang affiliations. Hernandez has denied any gang ties, Hodgson said.
"We feel we should still maintain caution even though we don't have any definitive notions at this point," the sheriff said.
He says Hernandez has been a model inmate but is being watched closely because other inmates might want to "make a name for themselves."
Hernandez's lawyers say the case against him is circumstantial and that he's eager to clear his name.
Hernandez signed a five-year contract worth $40 million with the Patriots last year but was released the day of his arrest.
Associated Press writer Michael Melia contributed to this report from Hartford, Conn.
Copyright 2013 The Associated Press.