LEALMAN — A 60-year-old ex-convict is accused of fatally stabbing his 75-year-old neighbor, a registered sex offender, in a Lealman mobile home park.Sylvester Johnson was arrested Saturday night on a charge of first-degree murder in connection with the death of William David Casey. Casey's body was found in his home Thursday morning by a neighbor who had come to bring him food.Johnson and Casey knew each other because both lived in the Palace Mobile Home Park, 2500 54th Ave. N. Investigators say Johnson went into Casey's mobile home sometime Wednesday night or early Thursday and stabbed him several times in the upper body.Pinellas County Sheriff's detectives say they linked Johnson to the crime through fingerprints found at the scene. They say the motive may have been robbery, as Casey's wallet was stolen. No weapon has been found, and the investigation continues.Florida's sex offender database shows that more than 100 men registered as sex offenders and sexual predators live in the mobile home park. It's on the western side of Interstate 275 at the 54th Avenue N exit, along Haines Road.Johnson is not a sex offender, but the state considers him a career criminal. According to Florida Department of Corrections records, he has been in prison five times since 1984 for burglary, drugs, sexual battery and dealing in stolen property convictions.He got out of prison in December after serving time on a cocaine charge, and was due to be on probation until 2020.Casey made news in June when he was arrested for trying to set up a sexual tryst with a 13-year-old girl and a Largo police detective posing as her mother.Casey's ex-wife had discovered a Yahoo Messenger account he was using named "nudeteeninga." She notified police, who began chatting undercover with Casey online.In the chats, Casey expressed interest in having sex with the mother and daughter and claimed he had molested a child in the past, police said.They arranged a meeting in Taylor Park in Largo, where Casey was arrested on charges of traveling to meet a minor for sex acts and enticing a parent to commit a sex act with a child.Detectives searched Casey's computer and found six photographs described as child pornography, netting more charges.Court records show Casey pleaded guilty to the charges March 19. He was sentenced to two years of community control, followed by three years of probation. On April 11, he registered as a sex offender at the Palace Mobile Home Park.Mike Brassfield can be reached at [email protected] or (727) 445-4151. Times researcher Natalie Watson contributed to this report.