BARNSTABLE— The man accused of killing Yarmouth Police Officer Sean Gannon is being held without bail at the Barnstable County Correctional Facility in Bourne.

Thomas Latanowich, 29, pleaded not guilty to murder and mistreating a police dog during an arraignment at Barnstable District Court on Friday.

A probable cause hearing for Latanowich, whose last known address was in Somerville, is scheduled for June 26.

Latanowich, sporting a moppy head of reddish hair and heavily tattooed arms, never looked up at the gallery jam-packed with police officers and media during the arraignment, keeping his head bowed.

It was not, by a longshot, his first time in a courtroom.

Latanowich, who previously lived in West Yarmouth, had well over 100 criminal charges in Massachusetts before Thursday’s arrest.

Records obtained by the Times indicate he has been arraigned and sentenced on more than 80 charges in Barnstable and Orleans District Courts since 2005. The charges run the gamut of criminal activity, including drug possession and trafficking, firearms possession, armed robbery, bombing and hijacking threats, strangulation, assault and battery with a dangerous weapon and vandalism.

A vast majority of the charges were either dismissed or not prosecuted.

In a 2009 case dismissed in Orleans, Latanowich had been charged with threatening to commit a crime and witness intimidation after allegedly accusing roommates of stealing a bag containing five handguns, telling one of them he “has killed people for much less.”

Gannon, a New Bedford native, was executing an arrest warrant for Latanowich at 109 Blueberry Lane in Marstons Mills on Thursday afternoon when he was fatally shot, allegedly by Latanowich. Gannon’s K-9 dog, Nero, was also shot and seriously wounded. According to Dennis Veterinary Hospital where he was initially stabilized, Nero, a 28-month-old Belgian Malinois  shot in the head and neck, survived surgery Friday morning.

The shooting occurred as Gannon was conducting a sweep of the attic in the house, according to the Cape & Islands District Attorney’s Office.

Latanowich was apprehended at the scene following a after a nearly two-hour standoff.

Latanowich was wanted for a probation violation after he missed a home visit and a drug test last week, according to information from the Massachusetts Probation Service.

Latanowich was sentenced on July 26, 2010 to four to five years in prison for assault with a dangerous weapon and related gun charges, according to the statement. He also was sentenced to five years of probation on multiple charges stemming from Barnstable Superior Court, including threatening to commit a crime, intimidation of a witness, knowingly receiving stolen property, possession to distribute heroin, possession to distribute a class D drug and possession of a firearm without a permit.

After serving his sentence, he was released on parole on Nov. 1, 2013. He violated his parole and was returned to custody until June 24, 2014. He then reported to probation, the term of which was scheduled to end Nov. 1, according to the statement.

Following the arraignment, Yarmouth Police Chief Frank Frederickson and Cape & Islands District Attorney Michael O’Keefe spoke with media on the steps of the courthouse.

“He (Gannon) was a remarkable young man,” said, Frederickson as he fought back tears. “He died doing what he loved.”

Asked to comment on Latanowich’s lengthy criminal record and how he seemed to quickly return to the community after many of the charges, Frederickson said “I have opinions on that, but I don’t want to share them right now.”

“That’s a very good question,” said O’Keefe when asked the same thing.

He also declined to comment on whether the death penalty would be appropriate for Latanowich.

“Our hearts are breaking with the Yarmouth Police Department and his family,” said O’Keefe.

At least 100 uniformed police officers and state troopers were present at the courthouse, including dozens of Yarmouth Police who occupied several rows of benches in the courtroom during the brief arraignment.

Hours before the arraignment, scores of spectators began to arrive at the county court complex – many holding American flags – waiting for Latanowich to arrive. 

— CCT Reporter Sean Driscoll contributed to this story