(CNN) — (CNN) -- A Boston grand jury has subpoenaed two more men to testify Thursday in its ongoing investigation into whether former New England Patriot Aaron Hernandez is connected to an unsolved double homicide in Boston last year.
Alexander Bradley and John Alcorn Jr. were ordered to answer the questions of a grand jury investigating the fatal drive-by shooting of Daniel Abreu, 29, and Safiro Furtado, 28, outside a Boston nightclub in July 2012.
Bradley, however, failed to appear before Superior Court Judge Joan Alexander in Hartford, Connecticut, on Tuesday to respond to the subpoena, and the judge issued an arrest warrant for him, according to court officials.
Bradley's New York-based attorney, David Jaroslawicz, told CNN he wasn't aware of the warrant or the subpoena and declined to say whether he has talked with his client about the grand jury matter.
Bradley filed a civil suit against Hernandez in federal court, saying the former football player shot him in the face, causing Bradley to lose sight in one eye, after the men visited a strip club in Miami earlier this year, according to the lawsuit.
In July, Bradley testified before a separate grand jury in Fall River, Massachusetts, that later indicted Hernandez on a charge of murder in the death of a friend, Odin Lloyd, June 17.
Hernandez pleaded not guilty last week to that charge and weapons counts.
Alcorn, 21, from Hernandez's hometown of Bristol, Connecticut, became involved in the investigation last month, when a friend of his, Jailene Diaz, told police a gun found in her car after a crash may have belonged to Alcorn and his friends, according to police documents obtained by CNN.
Law enforcement sources told CNN the .38-caliber handgun was identified by ballistics tests as the murder weapon in the unsolved Boston double homicide.
Investigators have also confiscated an SUV that law enforcement sources say is believed to be linked to the deaths. The vehicle is registered to Hernandez. It was found parked in the garage of Hernandez's uncle in Bristol after Lloyd was killed.
Alcorn is related to T.L. Cummings, a man who used to live at the same uncle's home. Cummings, who died in a car crash in June, was married to Hernandez's cousin Tanya Singleton. Singleton is jailed on a contempt of court indictment for refusing to testify before a grand jury in the Hernandez murder investigation.
Hernandez's lawyers have asked a federal judge in Miami to stay Bradley's civil lawsuit pending the resolution of the murder case against the fallen football star.