HOUSTON (KIAH) — A Waller County Precinct 3 Constable’s Office deputy was found dead in his patrol vehicle Thursday night in northwest Houston.

Investigators are trying to determine the cause.

First responders with the Harris County Sheriff’s Office were called to a person down in the 12000 block of West Little York at 9 p.m. Thursday after passers-by saw the patrol vehicle disabled with its lights on.

When deputies arrived, they found the deputy inside the vehicle not breathing.

As of Friday morning, investigators believe there is no sign of foul play and no obvious cause of death.

HCSO is investigating the incident and the Harris County Medical Examiner’s Office will determine the cause of death.