Maui police have arrested a 53-year-old Kahului man on charges of assault and burglary.
Officers say Lomae Lomae walked into his ex-girlfriend's home in Kahului and found her in bed with another man on early Friday morning. Lomae then became angry and struck the man in the head with a hammer.
Lomae had entered his ex-girlfriend's house without her knowledge or permission.
The victim was transported to the Maui Memorial Medical Center in critical condition.
Lomae's bail was set at $15,000.