Gerry McCracken, director of the agency, says no one could have predicted what happened on the weekend.
"This is an incident that really caught us all off guard," McCracken said Tuesday.
A 17-year-old boy charged with second-degree murder had been a client for "a long time," he added.
"It's not like he was new to us or anything."
Police said the body of the 61-year-old worker was found Saturday night at the home in Camrose, southeast of Edmonton.
The boy, one of three teens who lived in the home, was arrested the next morning 170 kilometres away in Vermilion, where officers also found the woman's stolen car.
He is to appear in court June 7.
McCracken identified the worker as Dianne McClements, who had been with the agency for 12 years. She worked with a variety of clients — from teens to disabled children and families.
"She's the type of person who would go out of her way any time, anywhere, and was always putting others first," he said. "She's going to be missed by a lot of people."
He said the home is run out of both sides of a duplex and houses older teens whose life skills need "fine-tuning." They learn how to budget, cook healthy meals and clean up after themselves. A staff member is on hand around-the-clock to provide support.
The teens must attend school, have a job, or both. McCracken said officials with the agency and the provincial government conduct a thorough review of potential clients, which includes examining whether they have violent pasts.
The home is fully accredited and staff are trained in crisis intervention. Most importantly, McCracken said, staff get to personally know the teens and learn if they have any "triggers."
Alternative living arrangements have been made for two other teens who were living in the home at the time of the killing, said Lisa Shankaruk, a spokeswoman with Alberta's Human Services Department.
She said the department has started reviewing its file of the youth charged with murder. It will look at whether he received appropriate services and supports.
Occupational Health and Safety will do its own review once police release the crime scene, said spokesman Barrie Harrison. It will examine the agency's assessments with regards to hazardous situations and its policies dealing with violence and staff working alone.
"It's our belief that we should exercise our due diligence and conduct our own investigation just to ensure that everything that could have been done from an employer's perspective to alleviate this type of thing from happening was in place," Harrison said.
The department is still investigating the death of 41-year-old Valerie Wolski, who was killed by a developmentally disabled man at a Camrose home in February 2011.
Officials were warned the man could be violent and posed a threat to anyone who cared for him.
Terrence Wade Saddleback was charged with manslaughter, but a judge last year found him mentally unfit to stand trial.
— By Chris Purdy in Edmonton