LANSING, Mich. — One frustrated client hurled a piece of concrete through the window of a welfare agency. Another threw her car keys at a welfare worker before being escorted away. At one point, a woman on public assistance even took a swing at a worker. As Michigan struggles with the highest-in-the-nation jobless rate, state workers who deal with unemployment, welfare and other aid programs say they have never been so overwhelmed — or so worried about their safety. Some clients have begun taking their anger out on the very people who are offering help. And caseworkers are seeking extra protection. "We are seeing it more and more as a dangerous situation,” said Amy Harrison, a caseworker who used to work for the state prison system, where she says she never felt as insecure as she does now. More than 15 percent of Michigan workers do not have a job. The dismal economy has also caused record demand for food stamps and public health care, forcing impoverished clients to wait hours for help in crowded office buildings. To make matters worse, a troublesome new computer system is also causing delays. It’s a recipe for conflict — or worse. "What is it going to take? Is it going to take one of us getting seriously injured or killed? I hope not,” said Laurie Massie, who works for the Department of Human Services. "I am replaceable as a state of Michigan employee. But I’m not replaceable to my friends and family.” Massie grew fearful when a 6-foot-4, 250-pound man walked into in her office in the Upper Peninsula demanding that his application for emergency assistance be processed. She told him she was helping another client who had an appointment. "He stood there. He stared me down,” said Massie, whose job is to determine if people are eligible for public assistance. The man began cursing and questioning why he was not being helped. He eventually left. Workers learned later that he had a history of armed robberies and aggravated assaults. About two out of every 10 Michigan residents receive some kind of state assistance. That’s 400,000 more than a year ago, and staffing levels at public-aid agencies are only slightly higher than before the recession.