A California man killed his two children before killing himself on Father's Day, WXIN reported.

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The bodies of the 40-year-old man, his 6-year-old daughter and his 18-month old son were found at a Santa Rosa, California, home Monday morning, KRON reported.

Sonoma County sheriff’s deputies said authorities were investigating a child custody violation between the man and his wife over the weekend before the bodies were found.

According to KRON, the man had custody of his children Sunday for Father’s Day and was to return them to their mother that night.

The children’s mother attempted to contact and locate the man and the children Sunday, to no avail.

Police were unable to get in contact with the man before visiting his home Monday and finding the three dead.

The man hanged himself, but police aren't yet saying how the children died, WXIN reported. According to KRON, there were no obvious signs of trauma or what caused the children's deaths.

The man and the children’s mother were married but separated for six months. The two were going through a divorce.