A 70-year-old man was arrested for sexual assault after he allegedly masturbated Sunday on a city bus next to a woman and four girls. 

Martin Nolter Jr., of no local address, was charged with fourth-degree sexual assault and appeared in Honolulu District Court on Monday. His bail is $1,000.

Police said the man got on the bus about 11 a.m. and sat next to the woman and her four nieces, then exposed himself and began masturbating before the group.

The bus driver called police after the man got off the bus. Patrol officers found him nearby and arrested him.

Police said he was arrested at Kamehameha Highway and Santos Dumont Avenue in Wahiawa.