HOUSTON (KTRK) -- Police are investigating the death at the downtown Houston jail off of Riesner.HPD is looking into what happened at the jail Sunday morning, after a 33-year-old inmate was found dead in his cell.Police say it all started around 1:30 Sunday morning."An individual walked into a convenience store on Houston's west-side, obviously intoxicated, being very disruptive to the clerk and then called for police," said Kese Smith, a spokesperson for the Houston Police Department.Police say the man was agitated and they arrested him for public intoxication and resisting arrest.Officers say the man continued to be disruptive once he was booked into jail."Punching at walls, very agitated after he was booked, he was examined by medical staff where he was cleared to be booked into jail," said Smith.Since he was combative, jailers put the man in an isolation cell and checked on him every 15 minute, starting at 2:30 am, then around 9:25 am he was found unresponsive in his cell.An autopsy will determine his official cause of death. Meanwhile, internal affairs, homicide and the District Attorney will all conduct a routine investigation as well.