( CNN ) The Boston doctor who was fatally shot Tuesday at Brigham and Women 's Hospital had treated the mother of the gunman , according to law enforcement sources and the shooter 's sister . Boston Police Commissioner William Evans said 55-year-old Stephen Pasceri of nearby Millbury came onto the second floor of the hospital , where the cardiovascular unit is located , and asked to speak with Dr. Michael Davidson . Pasceri shot Davidson when he came to the foyer between the waiting and exam rooms , according to Evans . Pasceri was found dead of what was `` clearly '' a self-inflicted gunshot wound , Evans said . Pasceri 's sister , Marguerite Joly , told the Boston Herald that Davidson had performed heart surgery on their mother , Marguerite Pasceri , who died in November . `` I think it comes down to the fact that my brother thought it was the doctor 's fault that my mother died , '' she told the Herald . `` I do n't know why my brother would blame him . I really do n't know why . '' Joly said Pasceri worked at the Milford-based company Waters Corp. and had graduated from Worcester State with a degree in accounting . He had four children , she said . `` We ca n't even wrap our brains around this , '' she said . `` There was no indication whatsoever that he would ever do anything like this . He loved his mom , and he loved her very much . He appeared to be handling her death well . '' `` I 'm in shock , I ca n't believe it . He was such a nice a man and ( he had a ) beautiful family . It does n't make any sense , '' Michelle Piselli , a neighbor of Stephen Pasceri , told CNN affiliate WHDH . `` It 's hard to process . '' Davidson , 44 , was the director of endovascular cardiac surgery at the hospital and an assistant professor at Harvard Medical School , according to the hospital 's website . Davidson lived in Wellesley , Massachusetts , and graduated from the Yale University School of Medicine in 1996 . `` Dr. Davidson was a wonderful and inspiring cardiac surgeon who devoted his career to saving lives and improving the quality of life of every patient he cared for , '' the hospital said in a statement . `` It is truly devastating that his own life was taken in this horrible manner . '' At a new conference Wednesday , colleagues remembered Davidson as a loving father and devoted friend who played guitar in a band with other physicians . They set up the Dr. Michael J. Davidson Family Fund in his memory . Davidson 's wife , Terri Halperin , also a physician , is 7 months pregnant . They have two daughters , ages 7 and 9 , and a son , who is 2 . One man taking his son to see a doctor said the scene at the hospital was hectic . `` There was nothing but police officers with guns drawn and everyone was yelling , '' witness James Pittelli told CNN affiliate WCVB . `` People were falling down , '' he said . `` Some were crying . It was a very surreal situation . '' CNN 's Tina Burnside and Lawrence Crook III contributed to this report .
The doctor , Michael Davidson , died late Tuesday evening . His wife is pregnant , and they had three children ages 9 , 7 and 2 . Police have identified the gunman as 55-year-old Stephen Pasceri .