A man and a woman sleeping outside early Tuesday morning were set on fire in Northwest Oklahoma City.

They are being cared for at the burn center inside the INTEGRIS Health Baptist Medical Center. OKCPD said the woman is in critical condition, but the man is expected to survive.

A 70-year-old man has been arrested and booked into the county jail. Police said they aren’t looking for anyone else in connection with the crime and the motive for the attack isn’t clear.

Taylor Self, Chief Communications Officer at the Homeless Alliance, said the incident is “heartbreaking.”

“Anytime someone is living outside, I think that they are super vulnerable,” she said, “14 to 21% of people experiencing homelessness are a victim of violence compared to 2% of the general population,” citing a 2014 study.

Self said anyone who needs shelter during the day can find it at the Homeless Alliance from 6:30 a.m. to 4 p.m. seven days a week.