KANSAS CITY, Kansas, May 22 (AFP) - Four 13-year-old boys and an 11-year-old boy were arrested on charges of sexually assaulting two six-year-old girls, officials reported here. Four of the five suspects were already under arrest, Wyandotte County District Attorney Nick Tomasic announced late Friday. The boys are charged with repeatedly assaulting the two girls -- twin sisters -- on May 15 at a day care center here. The adult day-care operator was at the site but apparently did not know of the crime. "This is as bad as any I've seen," said Tomasic, who has handled crimes against children in the past. The youths currently face charges of aggravated criminal sodomy and rape as juveniles -- but under a new 1998 could be charged as adults. "It is a possibility that one or more of the boys will be waived to adult status," said Assistant District Attorney Vicki Meyer. The girls did not tell their mother about the incident until the next day, and the girls were treated at the University of Kansas Medical Center, where doctors recovered physical evidence of rape and sodomy. When police interviewed the six boys at mid-week, two of the suspects "were remorseful and knew something very bad had happened," said Police Detective J.B. Smith. "One couldn't have cared less. He was a smart-aleck teenager," Smith said. None of the boys has serious juvenile records, though two had earlier been charged with shoplifting, police said.  