A South Side alderperson is urging residents to "stay safe" after a man relatives say was disabled and lived with cancer was found stabbed to death during an "extremely heinous" crime Monday afternoon at a South Shore home.Tony Landers, 61, was found unresponsive about noon after suffering trauma in a home in the 7100 block of South East End Avenue, police and the Cook County medical examiner's office said. A Tuesday autopsy found Landers died of multiple sharp force injuries, according to the office."It's an extremely heinous crime," Ald. Desmon Yancy (5th) told the Sun-Times. "I hope it's an isolated incident and would really like for people to treat it as such, but at the same time [I'm] asking people to stay safe and vigilant." Paramedics responded at the home, and Landers was pronounced dead at the scene. Relatives told ABC7 Landers was mute, had lung cancer and was struck in the head with some kind of object. The family also believes he knew his attackers, according to ABC7. "To kill an innocent person, a disabled person. He couldn't defend himself. He was weak. He was sickly," Melissa Winston, the victim's sister, told ABC7.The block where Landers was found was quiet Tuesday morning.About 10:40 a.m., three detectives wearing dark suits held clipboards over their heads to shield them from the rain and went inside the apartment building. A few minutes later they came out to talk to each other while one had a smoke before heading back inside for a few more minutes. They left about 11:30 a.m., pulling away in an unmarked police car. Melzenia Long, who has lived on the block for 10 years, said she saw people who appeared to be relatives gathering outside Landers' apartment complex after he was found Monday. "I'm so sorry [to hear] about that," Long said, after learning about the attack. Area 1 detectives are investigating. No arrests have been made.