Officer Thomas Schmidt was accused of holding down a shar-pei that had broken loose from its home while Officer Jeffrey Bolger cut the dog's throat.
Bolger, a Special Operations Section officer was charged with aggravated animal cruelty, animal cruelty and malfeasance. He was released on his own recognizance and suspended after the incident.
Schmidt was suspended Thursday, the Baltimore Sun reported.
The incident took place Wednesday after the shar-pei, Nala, escaped from her yard in Canton.
Nala's owner, Sarah Gossard, said she didn't know Nala had squeezed through a gate in her fence.
A woman noticed the dog was loose and tried to lead her home, but Nala bit the woman's hand. The woman had a superficial injury and called police to help capture the dog.
According to the police report, Bolger and Schmidt responded to the call. As Bolger got out of his police truck, a witness said they heard him say, "I'm going to [expletive] gut this thing."
Once the two officers had Nala restrained, witnesses said they saw Schmidt held her to the ground while Bolger slit her throat.
Baltimore police Deputy Commissioner Dean Palmere called the incident "outrageous and unacceptable."
"Internal affairs is continuing the investigation into the specifics of the incident," police spokesman Lt. Eric Kowalczyk said.