Police say they are still trying to figure out why a 24-year-old Ketchum man forced his way into a Northwest Boise home early Monday morning and beat up a man inside — but suspect that excessive drinking is part of the answer.

James B. Hansen is being held in the Ada County Jail on felony aggravated battery charge after Boise police say he forced his way in the front door of a home in the 4000 block of Plum Street (in the State/N. 36th streets neighborhood) just past midnight and attacked a man inside, who had to hospitalized for what have been described as serious but not life-threatening injuries.

Police say Hansen registered a .31 blood alcohol content (bac) percentage after taking a breath test at the jail after the arrest, according to police reports.

People at the home told police they heard someone making noise outside their house before ringing the door bell just after midnight. One person went the door, looked outside, and didn’t see anything. They yelled at the door, asking who was there, but got no answer, police said.

A short time later, two people inside opened the door to see what was going on when a man, later identified as Hansen, shoved it open and forced his way in, knocking over one of the people and attacking the other resident inside.

Someone inside called 911 and when police arrived moments later, they found Hansen inside the home standing over the resident, who was visibly injured, according to police reports.

Police say Hansen could not explain why he was there or why he attacked a man who lived there. Hansen was then arrested and booked into the Ada County Jail, where he took the breath test. A .31 bac is almost four times the legal limit for driving in Idaho, which is .08.

Police say they are still trying to figure out where Hansen was before he broke into the home. The people who live there, including the man who is in the hospital, told police they have no idea who Hansen is, according to reports.

Hansen is also charged with misdemeanor counts of battery and unlawful entry in connection with the case.

He will make his initial court appearance later Monday.

The crime of aggravated battery is punishable by up to 15 years in prison.