Kenneth Keith Kallenbach, an actor, comedian and long-running member of Howard Stern's "Wack Pack," has died in custody. He was 39.

Kallenbach, who was arrested in March for allegedly trying to lure an underage girl into his car, contracted pneumonia at a prison outside Philadelphia and died Thursday morning at a suburban hospital, his mother, Fay Kallenbach, said Friday.

Stern first reported the news on his Sirius Satellite Radio show Thursday.

The long-haired Kallenbach, whose goofball antics included attempting to blow smoke from his eyes, made dozens of appearances on Stern's show beginning in 1990. Stern once likened him to MTV's Beavis and Butt-head and wrote in his 1993 book "Private Parts" that Kallenbach was the "ultimate airhead."

More recently, Kallenbach, of Boothwyn, Pa., starred in commercials for ESPN's "Monday Night Football" and Stride chewing gum. He also appeared on Jay Leno's "Tonight" show on NBC and had uncredited parts in HBO's "Sex and the City" and the Tom Cruise film "Jerry Maguire."

Kallenbach was arrested in Upper Chichester Township, Pa., in mid-March on a charge of attempted child abduction. He had denied any wrongdoing.

His mother accused the Delaware County Prison of failing to provide adequate medical care, saying her son, who had cystic fibrosis, called her a few days before his death and begged her to intervene.

"They weren't treating him properly for his disease and this is how he contracted pneumonia," Fay Kallenbach said.

Pneumonia is a complication of cystic fibrosis.

Pablo Paez, spokesman for GEO Group Inc., the Florida-based company that runs the prison, declined to respond to Fay Kallenbach's allegation, citing privacy laws.

He said Kallenbach had been housed at the prison since March 27, and was taken to Riddle Memorial Hospital near Media, Pa., on Monday.

"We provide appropriate care for all the inmates at the facility," Paez said.

Copyright 2008 The Associated Press.