OSLO — A worshiper thwarted an attack on a mosque Saturday by a young man wearing a helmet and body armor, according to the Norwegian authorities and a witness. Hours later, the police said they had found a dead woman at a home linked to the assailant.

The police described the suspect as a young white man who appeared to have acted alone. He was arrested and charged with attempted murder in connection with the mosque attack near the capital, Oslo, and later with murder in connection with the dead body.

When the police made their way into a home where the suspect once lived, they found the body of a young woman.

“He is indicted for murder,” said Rune Skjold, a police spokesman.

During the mosque attack, the suspect was overpowered by a 75-year-old member of the congregation who sustained light injuries, said Irfan Mushtaq, a former director of the al-Noor Islamic Centre mosque and a board member who witnessed it.