PHOENIX -- The Chandler police union has blasted Maricopa County Sheriff Joe Arpaio in the arrest of a Chandler police sergeant accused in the death of a K-9.

READ: Reaction To Lovejoy's Arrest

"MCSO's decision to charge, arrest and book Sgt. Lovejoy is weak at best and completely outside the realm of being fair and reasonable," said Paul R. Babeu, President of the Chandler Law Enforcement Association.

Chandler police Sgt. Tom Lovejoy was booked into Maricopa County jail in Phoenix on Wednesday on a misdemeanor charge of animal cruelty after a two-week investigation into the death of 5-year-old Belgian Malinois "Bandit" who was left in a hot patrol car for more than 12 hours.

Lovejoy was released later Wednesday, said Capt. Paul Chagolla, a spokesman for the Maricopa County Sheriff's Office.

"We are confident Sgt. Lovejoy's actions do not rise to reckless behavior as required in charging and fail to meet the requirement for a criminal act," Babeu said.

"This incident was the needless and cruel death of an animal who was devoted to serve the public, and we are glad to see charges brought in this case," said Kari Nienstedt, Arizona State Director of the Humane Society of the United States.

CBS 5 News spoke with Lovejoy on the phone as he headed home from being processed. He said because of pending legal action, he had no comment.

"I am certain Sgt. Lovejoy has suffered greatly from leaving his police dog in a sweltering car," Sheriff Joe Arpaio said at a news conference.

"I do not relish the idea of compounding his sadness. However, Lovejoy must be treated like anyone else in similar circumstances," Arpaio said.

The sheriff's investigation showed Bandit was in Lovejoy's patrol car from about 9 a.m. to a little after 10 p.m. on Aug. 11.

The high temperature in Phoenix that day was 109 degrees.

During that time, the investigation found that Lovejoy ran errands for his wife, napped for a short time and later ate out with his wife. Lovejoy later found the dead dog in the car.

"As a Department, we respect and support the criminal justice systems and processes in place," Chandler Police Chief Sherry Kiyler responded in a statement.

"We remain saddened by the loss of K9 Bandit. At this time our internal investigation is continuing and further comment by our department would be inappropriate until the completion of this process," Kiyler said.

VIDEO: Officer's Family Expresses Remorse

Lovejoy faces up to six months in jail or up to $2,500 in fines.

He remains on desk duty with the Chandler Police Department pending an internal investigation.

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