Washington ( CNN ) -- Civil rights investigators for the Justice Department on Friday opened a federal probe into the controversial shooting death of a Saginaw , Michigan , man whose family says he had a history of mental illness . `` I can confirm the Justice Department now has an open investigation into the Saginaw shooting , '' said Mitchell Rivard , spokesman for Assistant Attorney General Thomas Perez of the Civil Rights Division . He spoke just one day after the Justice Department declined to comment on the case . Prosecutors and state police have already begun an investigation into the shooting death of Milton Hill . Hill had been had been arguing with officers in a parking lot next to a shuttered Chinese restaurant when he was shot , in full view of passing motorists and while he was holding some sort of knife . Saginaw County Prosecutor Michael Thomas said that the squad of police confronting him opened fire `` because apparently , at this point in time , he was threatening to assault police . '' Saginaw Police Chief Gerald Cliff said Hall was `` known to be an assaultive person '' with `` a long history '' of contacts with law enforcement , `` not only with police from our department , but with the county . '' Hall 's cousin , Mike Washington , acknowledged Hall had been jailed for minor offenses like vagrancy in the past , but , `` He was not violent . '' And Hall 's mother is growing impatient with the probe and questions why police opened fire so furiously on her son , whom she said was mentally ill. WJRT : Community questions police shooting . The July 1 shooting happened in a parking lot on West Genesee Avenue , a busy commercial strip on the north side of Saginaw . In a video purchased by CNN , shot by a motorist from across the street , the 49-year-old Hall is seen arguing with a half-dozen officers . For more than three minutes he walks back and forth , and at one time appears to crouch in a `` karate stance , '' according to the man who captured the scene . Police said Hall had just had a run-in with a convenience store clerk . On the video , he tells police , `` My name is Milton Hall , I just called 911 . My name is Milton , and I 'm p -- -ed off . '' When an officer tells him to put the knife down , he responds , `` I ai n't putting s -- t down . '' He appears unimpressed by a police dog , telling officers , `` Let him go . Let the motherf -- -ing dog go . '' Finally , he turns to the left of the frame , where another officer had moved out of view a short time earlier . It 's then that the police open fire with a reported 46 shots in a five-second hail of bullets .
Milton Hall was killed in a confrontation with police in Saginaw , Michigan . Prosecutors and police are looking into his death . Civil rights investigators for the Justice Department join the investigation .