The gunfire that Tuesday morning violated the purposeful calm of the cardiovascular wing of Boston's Brigham and Women's Hospital , late that night claimed the life of  Dr. Michael J. Davidson, a surgeon.

Police identified the suspected assailant as 55-year-old Stephen Pasceri of Millbury, Mass. 

According to police, a man entered the building on Francis Street shortly after 11AM and went directly to the second floor, asking to speak with Davidson.

When Davidson entered the foyer on the threshold of the examination area to meet his visitor, two shots rang out.

Speaking of Davidson at a mid-afternoon press conference, Boston Police Commissioner William Evans said, "He was targeted... There was something in the past that upset this guy" -- a reference to the shooter. 

Pasceri's mother, Marguerite, had been a patient of Davidson's. She died Nov. 15.

Loud voices were heard immediately before the shots were fired. 

Evans and hospital officials praised the fast response by police and hospital staff, who they said had been trained to respond to an "active shooter" situation.

Evans said police were on the scene within seconds after getting the first calls of shots fired and had the area secured within 15 minutes.

Police locked down the hospital and searched the second floor. They quickly found a man matching the shooting suspect’s description dead in an exam room. They said it was a “self-inflicted gunshot wound.”

According to investigators, a .40 caliber pistol was found on the floor next to Pasceri.

A graduate of Yale Medical School, Davidson was 44.