Dr. Michael Davidson’s killer didn’t just snap, there’s a darker story that led to that fateful day at Brigham and Women’s

Sephen Pasceri, 55, shot and killed cardiovascular surgeon Dr. Michael Davidson on Jan. 20, leaving the medical community in total shock, especially at Brigham and Women’s Hospital in Boston.

It became clear relatively soon that Pasceri’s reasoning for killing Davidson was because he was convinced that a drug prescribed to his mother following her surgery was what ultimately killed her. At first it seemed like Pasceri, who appeared to be a relatively normal guy, close to his family and involved in church, just snapped that day.

But Boston Globe‘s Evan Allen took a deeper look at the details of this man’s life with the help of court records and interviews with Pasceri’s family members, and what actually happened the day he walked through the hospital doors seems to be a reflection of a much deeper and troubled past.

“Really deep down, inside, he must have known that he was wrong for some of the things he did,” said his sister, Marguerite Joly. “I think he slowly lost his mind.”

Pasceri’s brother, John Pasceri, didn’t believe he was mentally ill, but his actions had caused issues in the past.

“When you were wrong, you had to suffer the judgments of Steve,” he said.

Video surveillance from inside the hospital shows Pasceri spending quite a bit of time walking around before approaching the reception desk and demanding to see Davidson, and eventually Davidson agreed to meet with him.

Davidson walked into Exam Room 15 with St. Jean, the physician assistant, at 10:25 a.m. Pasceri seemed angry, St. Jean recalled, but he never raised his voice. He sat at a small desk kitty-corner to Davidson; St. Jean pulled up a rolling chair next to the doctor.

Pasceri’s gun was holstered underneath his pants, the grip sticking up over his waistband but covered by his sweater. If it bulged, no one noticed.

Right away, Pasceri told Davidson to open the Internet, go to Drugs.com, and look up amiodarone.

“Are you aware that this drug is extremely toxic?” Pasceri asked, Sarah St. Jean said, pointing to the website. “Do you see all of the warnings on Drugs.com?”

Davidson explained he was aware of all the side effects but said Marguerite Pasceri did not react badly and was being monitored. Any drug, he explained, even an antibiotic, has potentially dangerous side effects.

Davidson spent the next 25 minutes in the exam room alone with Pasceri, continuing to discuss his upset, and then three shots were fired. As Allen points out, Davidson, after being hit in the hip and back reacted in a heroic way.

He fled the room, yelling, “Run, run, he’s shooting, he’s shooting!” Soon after, Pasceri put the gun in his mouth and pulled the trigger.

Pasceri’s family is now left knowing how troubled he really was.

“I wake up every morning, and I realize, ‘My god, my brother killed that man,’ ” Marguerite Joly said. “Every morning. And then I think about how they’re dealing with the day. How are they dealing with today?”

Despite the incredibly disturbing actions Pasceri displayed that day, moving forward, many people are spending more time reflecting on what a wonderful man, husband, father and doctor Davidson was. That seems to be a better use of time.

According to Brigham spokeswoman Erin McDonough, a fund has been set up to support his family.

“There are no words that can adequately describe the depth of the loss the Davidson family and the BWH community are experiencing as a result of a senseless, selfish act of violence,” McDonough said in a statment, according to the Globe. “We encourage anyone whose life has been touched by Dr. Davidson or who has been moved by his story to support the Davidson Family Fund” at www.rtn.org/davidsonfund.