Hernandez is scheduled to be arraigned on two murder charges May 28.
Prosecutors say Hernandez shot Daniel de Abreu and Safiro Furtado as they sat in a car in the city’s South End in July 2012 after a chance encounter at a nightclub.
The shooting apparently was unrelated to the killing last year of Odin Lloyd, whose body was found near Hernandez’s home. Hernandez has pleaded not guilty in that case.
Prosecutors are also seeking assistance from tattoo artists who may have inked Hernandez’s right arm between February 2012 and June 2013. Hernandez is known to have traveled to California, Florida, Connecticut and Rhode Island in that period. The tattoo artists are considered witnesses, not suspects.