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 don't know why my brother would blame him. I really don'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 can'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 can't believe it. He was such a nice a man and (he had a) beautiful family. It doesn't make any sense," Michelle Piselli, a neighbor of Stephen Pasceri, told CNN affiliate WHDH
. "It's hard to process."
'A wonderful and inspiring cardiac surgeon'
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."