How can an officer confuse a firearm for a taser?

Former police officer Kim Potter has been charged with second-degree manslaughter after fatally shooting 20-year-old Daunte Wright in the Minneapolis suburb of Brooklyn Center last weekend. He was pulled over when driving, then a scuffle ensued, and Potter pulled out her gun and shot him. She resigned afterward, and said she thought she was using her taser.

But how is it possible that an officer can confuse a gun and a taser?

“When you grab a taser, it feels like a handgun. It's got a pistol grip. They weigh about the same in many cases, some cases less, depending on what type of firearm that officer is carrying to begin with,” explains Deputy Sheriff Edward Obayashi of the Plumas County Sheriff’s Office. “But in the heat of these incidents and the stress level, it's not uncommon for an officer to lose sensory perception about the weight of a gun, what’s in his or her hand.”