A man in Pennsylvania killed his son and two grandchildren by setting their house on fire while they were sleeping inside, police said Tuesday.

The man, identified as 67-year-old Jafar Afshar, also died in the fire. His death was ruled a suicide. The triple murder-suicide incident took place Friday in an apartment in Steelton.

At a press conference Tuesday, Dauphin County Coroner Graham Hetrick said Jafar killed his son, 36-year-old Saeed Afshar and two grandchildren – an 8-year-old boy and a 5-year-old girl – by pouring accelerant inside the home and lighting it.

The corner ruled the deaths as homicide. The cause of death reportedly was thermal burns and smoke inhalation, Penn Live reported.

Authorities did not reveal the motive for the killings, but Hetrick said Jafar Afshar was showing "abnormal behavior" prior to the fire, according to WGAL. The identities of the children were not released. 

An online fundraiser was started for the children's mother. It remains unclear where the mother was at the time of the incident.

"A terrible tragedy occurred in our family on Friday August 6th, when my cousin's 8-year-old son and 5-year-old daughter passed away in a fire inside their home. We are all deeply devastated by this loss and are trying to do everything as best as we can to help my cousin and her family get through this. Both financially & emotionally," the creator of the GoFundMe page wrote.

The incident is the first triple killing in Dauphin County in 20 years.

Last month, a man fatally shot his two children before setting the house on fire. The man then shot and killed himself. The Kuhl House Fire Department arrived at the scene and found three bodies in separate rooms. 

If you have thoughts of suicide, confidential help is available for free at the National Suicide Prevention Lifeline. Call 1-800-273-8255. The line is available 24 hours, every day.

crime scene Representational image Photo: Getty Images/Jonathan Alcorn