The charred body of a woman was found early Tuesday in the trunk of a rental car parked in a forest in Numazu, Shizuoka Prefecture.

Police identified the woman as 53-year-old Rei Imamura, the head nurse at a hospital in Yokkaichi, Mie Prefecture.

A man with severe burns who was found nearby was identified as 65-year-old Kenji Nakajima, her brother-in-law.

Nakajima is in critical condition.

According to police, Imamura's elder sister, 55, had consulted her about the possibility of divorcing Nakajima.

After Nakajima learned that Imamura had written her sister to advise her on how to file for divorce by consent and how to hire a lawyer, he threatened his sister-in-law in a letter last month that said, "You tried to separate us. I will kill you."

Nakajima, a resident of the town of Kyonan, Chiba Prefecture, was visiting Imamura to look for his wife, who had recently run away from home, the sources said.

Around 8:50 p.m. Monday, one of Imamura's colleagues found blood stains on the ground in the hospital's staff parking lot. Police said the colleague also noticed that the door to Imamura's car was ajar.

Around 2:30 a.m. Tuesday, a witness saw a burning car and a man on fire in the forest in Numazu, police said.

The rental car belongs to a company based in Yokkaichi and has Gifu Prefecture license plates, police said.