An elderly dementia patient in South Korea was sentenced to 20 years in prison on Friday for setting a fire at a hospital for the elderly that killed 22 people.

The 81-year-old man was convicted of arson and manslaughter, according to Gwangju District Court spokesman Han Ji-hyeong.

The man denied responsibility for the fire at a hospital in southern South Korea in May, but the court gave weight to security camera footage and the testimonies of hospital employees to establish that he set fire in a hospital room, Han said.

The incident raised concerns about lax fire regulations because it happened when the country was undergoing soul searching over public safety following April's ferry sinking that killed more than 300 people.

After investigating the fire, police concluded that the death toll rose because the hospital did not have sprinklers and did not have enough employees on night duty at the time of the incident.

The South Korean government in August announced tightened safety rules for senior facilities, requiring the hospitals to install sprinklers within the next three years and strengthen personnel on night duty and on weekends and holidays.