(CNN) On its surface, the photo looks strange: Portland police officers getting ready to cart off protesters whose heads are covered in hoods and earmuffs

Critics say it's a shocking display of strong-handed police tactic. Officers counter they have a perfectly good explanation.

Here are the two sides of the story behind a remarkable protest photo:

What happened

The incident happened Wednesday outside a US Immigration Customs and Enforcement Facility in southwest Portland. Members of the group End Deportations Now showed up to block a bus taking undocumented workers to a detection facility.

Five protesters formed a "chain" using a device known as a "sleeping dragon." In it, protesters place their hands through pipes and either cuff themselves or zip tie their hands. In this case, the pipes were wrapped in duct tape with the words "Stop the deportations."

Police arrived and put protesters in hoods and earmuffs before they set about cutting the pipe.

What police say

Cops say there was no way for them to know if the pipe under the tape was metal or plastic. If it was metal, it would cause sparks when they cut through it. So, for the safety of the protesters, officers placed hoods on their heads. "These are the same protective hoods firefighters wear going into a fire," police spokesman Sgt. Chris Burley told CNN. "They are made of fire retardant material should sparks fly into the faces of protesters." Officers also placed ear muffs to minimize the loud noise from the tools, he said. "All of these actions were taken to ensure the safety of the people who were fitted into this 'sleeping dragon' device." Burley said the protesters bound themselves using yarn, chicken wire, bolts and chains.

What protesters say

Amina Rahman, one of the protesters, says she doesn't buy the explanation that the hoods and earmuffs were for demonstrators' protection. She told The Oregonian she didn't hear any loud noises from the tools. It was a "scare tactic," she told the paper