Kelly A. Frank, a 43-year-old painter who had worked on David Letterman's Montana ranch, was arrested Thursday for plotting to kidnap the talk show host's 4 1/2-month-old son and his nanny and hold them for $5 million ransom.

Local authorities were tipped off when Frank allegedly approached someone about the job and the person notified police. Frank was arrested and is being held on charges of soliciting help in a kidnapping. He has also been charged with a felony theft for overcharging Letterman for painting his ranch and obstructing justice for lying to an investigator.

According to an affidavit filed in the case, Frank told the contact that he had a key to Letterman's residence and he knew where the baby slept. He indicated he would kidnap the nanny and the child 'so that she could take care of the child' after Frank abducted the infant.

Letterman and his girlfriend, Regina Lasko, released a statement thanking the FBI and local police for their help in the case. 'We will be forever grateful for their tireless efforts and determination to vigorously pursue this situation,' the statement read.

Frank is presently being held at Pondera County on $600,000 bail. No date for his first court appearance has been set at this time.