A San Diego-based family of 4 was found dead at their home in San Diego on Tuesday morning, baffling investigators.

A couple, their 9-year-old daughter Emily and her elder sister Priscilla were found dead. While three were found dead in a swimming pool, the fourth member was found dead in a bath tub. Police said they are still investigating their deaths.

San Diego police Lt. Ernie Herbert said the police suspect that one of the family members killed the other 3 and then committed suicide. The motive hasn't been determined yet.

Friends and neighbors of the family said they were shocked by the incident as there was nothing unusual about the family.

They said the couple was hard-working and owned a towing business. Emily is easy-going and loveable. Seventeen year old Priscilla was set to graduate next month from San Diego’s High Tech High school.

Jose Villa, the mother's stepfather said he and his wife picked up Emily from school Monday. Also, Priscilla's classmate Jasmund said everything seemed normal when he saw the family at a pool party held at their home on Saturday.