It was a parent's worst nightmare — a complete stranger following a family home and molesting a child at knifepoint in her bed. Authorities say such a crime, which played out in St. Louis County last weekend, is exceedingly rare.

Still, the attack of an 11-year-old girl in the Mehlville area has raised concern about stranger danger.

Relatives told the St. Louis Post-Dispatch that the suspect, 40-year-old Larry Alverson, has serious psychological issues.

Alverson, of Belleville, Illinois, is a recent parolee. He was arrested Tuesday and is jailed on $1 million bail on charges of first-degree burglary, statutory sodomy of a child less than 12 years of age and other counts.

Experts say strangers are involved in sex crimes in only about one of every 14 cases.