DENVER After four people were stabbed two fatally along the 16th Street Mall this past weekend, Denver7 Investigates has been digging into the suspect's criminal history and background.On Saturday, three people were stabbed along the 16th Street Mall, with a fourth stabbing on Sunday near Union Station. Two people died of their injuries one of the Saturday victims and the Sunday victim, the Denver Police Department (DPD) reported. The suspect, identified as 24-year-old Elijah Caudill, was arrested Sunday after police say he was spotted running with a long, "butcher-style" knife.Don Caudill, Elijah Caudill's grandfather, spoke to Denver7's Jaclyn Allen via Zoom, saying his family has received online backlash following the crimes."I've been bombarded with this since it came out on the news. People have searched my name up on the internet and sent me messages, hateful messages. People don't know the facts," said Caudill.Don Caudill said his grandson has struggled with substance abuse, including fentanyl and heroin."I do know he hears voices, imagines things, and he does self-medicate on the street," said Caudill. "He was taking ADHD meds, and he quit because he didn't think he needed them. He got out there on the streets and started using drugs to medicate himself."After that, Caudill said his grandson served years in jail with severe, untreated mental health issues. "When he was in jail, I feel that the jail should have seen that he had mental problems. They don't," said Caudill, who said he has also dealt with mental illness. "Mental health patients, we need help. I'm living with this. I am working on myself. We need help, damn it, plain and simple, and there should be more help.Studies have shown the vast majority of people with mental illness do not commit violent crimes, and that most people who are violent do not suffer from mental illness.Denver7 Investigates has covered concerns over the state's mental health resources and laws, including a new law that requires judges to dismiss criminal charges when a defendant is deemed incompetent and nonrestorable.But Caudill said in this case, the system failed his grandson, contributing to what happened last weekend."I don't know all the facts that going on right now," he said. "I know he does have mental problems, and I know that there are a lot more people in jail that do have mental health problems."