In May, a woman filed a federal civil rights lawsuit against the Detroit Police Department for shooting her three dogs back in January, according to an investigation by the Libertarian magazine Reason released on Wednesday.

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Through public records requests of police reports, Reason found that one of the officers involved in the shooting has killed 39 dogs in his career. The requests also revealed that another DPD police officer, not involved in aforementioned the lawsuit, killed 67. 

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Records requests by Reason also found that the New York Police Department killed nine dogs in 2014, the Los Angles Police Department killed eight dogs in 2015, and Chicago police officers shot at an animal 84 times in 2015 and 2016.

There is no comprehensive national database for dogs shot by police, but a Department of Justice official called police killings of dogs an "epidemic." Laurel Matthews, a supervisory program specialist with the Department of Justice's Community Oriented Policing Services told Police magazine in 2012 that about 25 to 30 pet dogs are killed by police everyday. 

There is also a Facebook group with more then 16,000 followers dedicated to "Dogs Shot by Police" and a website called the "Puppycide Database" that attempts to track cases. However, we don't know exactly how many dogs are killed by police each year. 

ATTN: talked to two experts about the police shootings of dogs and why they happen. 

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Dr. Randall Lockwood, the senior vice president of forensic sciences and anti-cruelty projects at the American Society for the Prevention of Cruelty to Animals has conducted trainings for police officers on how to handle issues with dogs. He told ATTN: that dog shootings are common. 

"Yes, there are reports of such incidents on a daily basis," he said. "The Department of Justice recently hosted a round-table meeting to review the issue and will be assembling a report in the coming months." 

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Lockwood said that sometimes police have a legitimate reason to shoot dogs, but other times a lack of training is to blame. 

"Sometimes dogs are being used as weapons against police, but often such actions are related to lack of training on how to accurately assess the risk posed by a particular dog and how to effectively respond to encounters using the minimum amount of force necessary to prevent injury to the public, the officer or the dog," he said. Tennessee, Colorado, Illinois , Ohio, and Texas have passed laws that require dog training for police officers, according to Lockwood. 

Based on available public records, the ASPCA estimates that half of police firearm discharges happen in dog shootings. 

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Nathan Robinson, a Harvard doctorate student of sociology and editor of the magazine Current Affairs, wrote an opinion piece in The Washington Post last year about dog shootings. He told ATTN: that some police officers will kill a dog before thinking about other alternatives. 

"While there are valid instances in which deadly force is justifiable on a dog, like all uses of force it should only be as a last resort," he said. "The problem here is that police shoot dogs [instinctively], as a first resort rather than a last resort."

Robinson said that police officers should receive "serious instruction on how to deal with dog encounters" to prevent dog shootings. 

"After all, dogs are people's family members," he said. 

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