The high in Houston on Aug. 26 was 95 degrees.
When the officer returned from lunch, the dogs were all "in distress," said Kathy Barton, spokeswoman for the city health and human services department. Two were dead when the officer returned to the shelter. The other six died that afternoon.
"I do not believe we are dealing with a cruelty issue," Barton told the Houston Chronicle. "We are dealing with a mechanical issue or a human failure issue."
The officer has been assigned to duties within the shelter while the investigation is conducted.
"In any other work setting, an employee who screws up this bad would be fired," activist Sherry Nassar said in an e-mail to the newspaper. "BARC is a heartbreaking place to work -- most people couldn't do it day in and day out. But there are shelters in this country, an increasing number of them, that are able to attract and keep good employees who stay for years because the culture is humane and requires humane treatment of the animals."
Kelly Cripe, another activist, said the district attorney's office should consider bringing an animal cruelty charge against the officer.
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