The store is owned by relatives of Shuff, who lives in a house on the same property in the 12200 block of Baugher Road but does not work in the store, Tobery said.
When police got to the store, Shuff was back inside, and authorities were concerned he might have had access to weapons.
Several attempts to negotiate with him were unsuccessful, deputies said.
During the next 30 minutes, Shuff ran outside then went back into the market. When he emerged a second time, he went toward a deputy who is a canine handler, who ordered him to stop, Tobery said.
Shuff ignored the order, and the police dog, a German shepherd from Czechoslovakia named Eno, went for his chest, he said.
He grabbed the dog and bit a chunk bigger than a quarter from Eno's ear, Tobery said.
A second deputy was thrown into the air and landed on his back on the ground, he said.
Two other deputies also were injured in the prolonged struggle, during which deputies used pepper spray and other defensive tactics to subdue Shuff, Tobery said.
The three deputies were treated for minor injuries at Frederick Memorial Hospital and released, he said.
Shuff was treated for dog bites and seen by doctors at Frederick Memorial Hospital on an involuntary emergency mental evaluation, deputies said.
He was committed to a mental facility, deputies said.
Eno was treated by a veterinarian, who did reconstructive surgery, deputies said.
Tobery said he and his fellow deputies appreciated the unusual sacrifice Eno made for them.
"I've heard of K-9s being hurt and killed in the line of duty, but this is the first time I've heard of anything like this, the dog actually being bitten. It's a sad thing. The dog was doing his job, what he was trained to do," he said.
Charges were filed against Shuff later Monday, according to a Frederick County court commissioner. They include three counts of second-degree assault on sheriff's deputies, three counts of false imprisonment, three counts of resisting arrest, two counts of animal cruelty, and one count of felonious malicious destruction of sheriff's office property, according to a press release.