Honolulu police have arrested two siblings after they allegedly assaulted a 67-year-old man in Kaimuki.

Police said a 52-year-old man struck the victim with a piece of lumber at about 8 a.m. Thursday, causing head injuries.

The suspect’s 45-year-old sister jumped in the altercation and allegedly grabbed the victim’s groin area, according to police.

The suspects and victim are strangers.

Police officers responded and arrested the man on suspicion of second-degree assault and his sister on suspicion of third-degree assault.

The motive of the assault is under investigation.