JENKS, Okla. (AP) — Police in the Tulsa suburb of Jenks are trying to determine why a 36-year-old man fatally shot his 8-year-old and 10-year-old sons before killing himself, a police spokesman said Tuesday.

“Now we're deeply involved in trying to determine a motive,” police spokesman Sgt. Eric Bowdle said.

Police said Thang Khen gathered his four children in the garage of their home Saturday afternoon and fatally shot 8-year-old Peter Khen and 10-year-old Samuel Pau. Police said a 9-year-old fled into the house and an infant was unharmed.

The shooter’s brother called 911. Bowdle said a multiple family members lived in the home..