CHATHAM, N.H. — A hiker suffered a serious head injury after climbing a fire tower atop Mount Kearsarge North in Chatham to take photos, the New Hampshire Department of Fish and Game said.

The 25-year-old hiker from South Portland, Maine, tumbled Sunday afternoon from the top of the stairs and landed at the base of the tower, the department said.

The hiker’s companion rendered first aid and another hiker who witnessed the fall called for help.

An Army National Guard helicopter was summoned after officials determined the injured hiker’s condition was worsening. The hiker was extracted nearly three hours after the fall.