BARNSTABLE, Mass. (AP) — A man charged with killing a police officer and described by authorities as a violent career criminal was ordered held without bail Friday.

Thomas Latanowich hung his head throughout his brief arraignment in Barnstable District Court, speaking only to answer “yes” when the judge asked if he understood the proceedings.

Not-guilty pleas to charges including murder were entered on his behalf, and the judge said she would appoint a lawyer to represent him. Court records showed Latanowich had been charged with more than 100 crimes in the past and was on probation after completing a prison sentence in 2014.

Latanowich shot Yarmouth K-9 officer Sean Gannon on Thursday while he and other officers were serving an arrest warrant for a possible probation violation at a home in Barnstable, on Cape Cod, police said.

Gannon, 32, was taken to Cape Cod Hospital, where he was pronounced dead.

Gannon’s dog, Nero, also was shot. Dennis Veterinary Hospital posted on Facebook that Nero was shot in the face and neck but had been stabilized and faced surgery Friday.

The loss of Gannon has stunned the picturesque community of Yarmouth, next to Barnstable.

“Sean, remarkable young man. We refer to him as the Tom Brady of the Yarmouth Police Department,” Chief Frank Frederickson said outside court. “He’s gone. He died doing what he loved. He’s going to be sorely missed.”

Gannon, an eight-year veteran of the force, was married and a graduate of Bishop Stang High School in Dartmouth and Westfield State University. He previously worked for the Nantucket and Stonehill College police departments.

Republican Gov. Charlie Baker said he conveyed his condolences in a phone conversation with Frederickson on Friday.

“The sadness and heartbreak that carried in his voice says it all,” Baker said. “This is an incredible tragedy and a huge loss, and we all expect justice to be served for this heinous crime and trust that our judicial system will hold his murderer accountable to the highest degree.”

Baker held a moment of silence for Gannon before a news conference on Friday in which he signed a bill that calls for major reforms in the state’s criminal justice system. Baker also ordered all U.S. and state flags on state buildings lowered to half-staff in honor of the fallen officer.

A steady stream of residents arrived at the police station Friday to offer condolences. Many placed flowers in front of the station and on Gannon’s cruiser. The Yarmouth Police Foundation appealed for cash donations to help the officer’s family.

According to Cape and Islands District Attorney Michael O’Keefe, Latanowich’s last known address was in Somerville, outside Boston.

Latanowich, 29, has been arrested numerous times, according to police and court records, though many of the charges were later dismissed.

O’Keefe said the last prison time Latanowich served was a four- to five-year sentence on gun charges. The prosecutor expressed frustration that prior charges had not resulted in more lengthy sentences.

Latanowich’s next court date was scheduled for June 26.