By Jeremy Ross

CHICAGO (CBS)– The first full day back at work for staff at Mercy Hospital since the shooting seemed quiet, but the psychological impact for those who were inside the hospital at the time of the shooting may not be apparent for weeks or months down the line.

Outside the hospital, memorials have been put up for the three victims.

CBS 2’s Jeremy Ross reveals how the hospital is keeping watch on the mental well-being of staff.

Hospital workers like Joe Lagreco returned to Mercy Hospital for their first full day back since Monday’s tragedy that claimed the lives of Dr. Tamara O’Neal, Pharmacy graduate Dayna Less and Chicago police officer Samuel Jimenez.

“You’re going though sadness (and) you’re going through anger,” he said, adding that sleep was hard to come by the night of the shooting.

Dr. Michael Davenport of Mercy Hospital said the hospital is putting measures into place to help staff cope with the workplace tragedy.

“There’s a lot of people who are blaming themselves thinking they could have done more to help,” Davenport said. “My other colleagues have expressed they’ve not been able to sleep.”

He said the hospital is monitoring for PTSD, which can involve anxiety and depression.

The American Psychiatric Association says PTSD affects approximately 3.5 percent of all U.S.  adults. Symptoms need to be present for more than a month for a diagnosis.

Davenport said there are 1,600 hospital employees, including a few hundred employed in the areas where the shooting took place.

A handful have not come back to work yet, but most have

In a place where birth and death are relativity routine — the hope is health care workers are more resilient to the possible psychological aftermath.

“We want to come to work, and that’s healthcare people–that’s what they do,” Davenport said.