Police spent most of the day collecting evidence from a house on Maxwell Street where the brothers lived with their parents.
Investigators say several family members were home and witnessed the murder.
Hanford police say after Ayala shot his brother in the neck -- he ran from the house, but he was caught soon after.
Police say while there were children inside the house at the time none of them witnessed the actual crime.
If Samuel Ayala is formally charged by the DA's office he will likely be arraigned on the murder charge next week.