A convicted sex offender was rearrested after police learned he stalked a Pennsylvania boy, including sending him letters and even moving next door to him, NBC Philadelphia reported.

Clyde Ruppel, 73, was arrested Tuesday on charges of stalking and drug possession following an investigation into his alleged staking of an 11-year-old boy from Allentown.

According to a probable cause affidavit, Ruppel, who was convicted of rape in 1996, began stalking the boy two years ago and left signed letters on his father's windshield. The letters, which had peach-colored rose petals attached to them, invited the boy over for "all male nights," the affidavit said according to the station.

For months Ruppel followed the boy, driving slowly behind him as he walked home, police said. The boy's father repeatedly warned the elderly man to back off but he continued his advances and moved into an apartment next door to the child's family, NBC News reported.

By that time Ruppel was watching the boy play outside, police said. The father finally received peace of mind when Ruppel was arrested for public harassment in November. But Ruppel was later released.

He was arrested again for the stalking charges after a deeper investigation last week uncovered the allegations, the station reported.

In addition to his 1996 conviction, Ruppel was convicted for indecent assault in 1976 and has another conviction also for indecent assault.  

Police slapped extra drug-related charges on Ruppel after a search of his apartment, now vacant, turned up marijuana plants. He was ordered held on $35,000 bail.