HONOLULU -- A 24-year-old nursing home worker was indicted Tuesday in a sexual assault case on elderly women in his care.

Authorities charged Mark Genetiano with six counts of sexual assault involving four victims -- the youngest was 89. All of the patients suffered some level of dementia, officials said.

Prosecutors said coworkers told authorities that Genetiano undressed the woman, touched their nipples and laughed when they fought him.

He is being held on $250,000 bail and faces an automatic prison term if convicted.

Officials at the nursing home, Kahala Nui Senior Living Community in Waialae, said they fired Genetiano after their own internal investigation.