Yarmouth police officer Sean Gannon was shot as he attempted to serve a warrant to a suspect with a long criminal history.

The man accused of the murder of Yarmouth Irish police officer Sean Gannon has pleaded not guilty to the crime.

A large number of Gannon’s Cape Cod fellow police officers gathered in court to look on as Thomas M. Latanowich, 29, pleaded not guilty to shooting the K-9 officer in the head as he attempted to serve a warrant.

Latanowich has a lengthy criminal history and Gannon was serving a warrant after the 29-year-old broke the terms of his probation.

Gannon’s dog Nero was also gravely injured in the shooting and underwent surgery after being shot in the face and neck.

Authorities allege that Gannon was shot by Latanowich at 2.30 pm on Thursday as he entered the attic in pursuit of the suspect. Latanowich was ordered held without bail in court and was led away by police officers.

Read more: Video of Irishman's murder in Trafalgar Square released by British police

With a heavy heart 💙, our condolences go out tonight to our brothers & sisters of the @yarmouthpolice & to Officer Sean Gannon's family & friends. We are also praying tonight for the recovery of Officer Gannon's K9 partner, who was also injured in today's tragic incident.#LODD pic.twitter.com/9ITeLFi3bq

— Mass State Police (@MassStatePolice) April 13, 2018

Gannon and two other police officers were searching a home at 109 Blueberry Lane in Marstons Mills, a village in Barnstable, when the fatal shooting took place. They were seeking to arrest Latanowich for violating his probation for a case in 2010 when he pleaded guilty to drug and gun charges. He was taken into custody again within an hour of the shooting.

“Sean was a wonderful, wonderful young man,” said Yarmouth Police Chief Frank Frederickson. “We’re going to miss him terribly.”

Hearse carrying the body of fallen #Yarmouth Police officer Sean Gannon has arrived at the Medical Examiner's office in #Sandwich pic.twitter.com/rqU8gi1Ys5

— WBZ | CBS Boston News (@wbz) April 13, 2018

Massachusetts Governor Charlie Baker also extended his condolences:

“I am heartbroken to learn of the passing of Officer Gannon and my thoughts and prayers are with his family, loved ones, and the Yarmouth Police Department after this tragic loss,” he said in a statement.

Read more: Irish dad jailed on family trip to US for visa overstay 22 years ago

Somber moment as fallen officer Sean Gannon’s cruiser - lights flashing - is towed from the neighborhood where he was killed in Marstons Mills. #WCVB pic.twitter.com/VoN1yB4eGU

— John Atwater (@AtwaterWCVB) April 13, 2018

Latanowich is said to have an extended adult criminal history with 28 cases against him in Barnstable district court alone. This includes a four-year state prison term and more than 110 entries on his criminal history.

Charges include a 2016 arrest in which he allegedly strangled a pregnant woman and vandalized her vehicle.

Gannon was a well-known K9 officer who also volunteered in the Big Brother project. He had served for eight years, initially joining Stonehill College Police Department and serving as a summer officer in Nantucket before joining Yarmouth Police Department. 

Fallen police officer Sean Gannon.