BARNSTABLE — Sean Gannon was a rising star in the Yarmouth Police Department, sent with two other officers Thursday afternoon to a quiet neighborhood to carry out an arrest warrant.
Thomas M. Latanowich was a career criminal with more than 100 cases to his name, a litany of charges for stabbings, drugs, and gun offenses. He was unwilling to go quietly, authorities said.
When Gannon, 32, tried to apprehend Latanowich, chasing him into the attic of his Cape Cod home, Latanowich fatally shot the officer in the head, according to a law enforcement official.
Court records show that Latanowich, 29, had been arrested repeatedly in recent years, including on charges of strangling a pregnant woman and stabbing a man at a traffic light. He was on probation for gun offenses, but he had largely avoided jail time since 2014.
The realization that someone with such an extensive criminal past had remained free, despite repeated encounters with authorities, ignited outrage among grieving members of the law enforcement community Friday.
“It’s terrible, it’s terrible,” Cape and Islands District Attorney Michael O’Keefe said Friday. “Is it frustrating? Of course it is. He, like many criminals, had guns. How did he get the firearms? He’s a criminal.”
With roughly 100 uniformed officers looking on, Latanowich was charged in Barnstable District Court with killing Gannon, a Yarmouth police officer for eight years. He pleaded not guilty, and was ordered held without bail.
Prosecutors did not provide details of the shooting, which happened Thursday around 2:30 p.m. at Latanowich’s home on Blueberry Lane in Marstons Mills, a village of Barnstable. A police report on the incident was sealed.
Latanowich, who was apprehended within an hour of the shooting after authorities surrounded the home, kept his head down during his arraignment and did not speak. A court officer gripped his right arm, which is covered in tattoos.
Afterward, Yarmouth Police Chief Frank Frederickson recalled Gannon as the “Tom Brady” of the department.
“He’s gone,” Frederickson said, speaking softly and at times haltingly. “He died doing what he loved. And he is going to be sorely missed, and we have a devastated community, family, and police department.”
The presence of police officers in the courtroom was meant to send a message, he said. “We know who you are. You didn’t get all of us,” he said. “So your day will come.”
Gannon’s police dog, Nero, was also shot in the face and neck during the attack and was in serious but stable condition Friday night, said Mike DeFina, a spokesman for the Animal Rescue League of Boston.
Police were looking to arrest Latanowich for violating his probation for a 2010 conviction for drug and gun charges. Latanowich, who had listed his address in Somerville and transferred his probation supervision to Middlesex County, was not at home for an April 4 visit from a probation officer and then failed to show up a day later to take a required drug test, according to the Massachusetts Probation Service.
That prompted Middlesex authorities to seek his arrest for the probation violation, O’Keefe said.
Latanowich was believed to have a brush with the law on April 3 in Everett, when a state trooper tried to pull over a car authorities think was driven by Latanowich on Route 1 northbound.
The car was found parked and unoccupied in a nearby cemetery. State and local police, aided by police dogs, searched the area but didn’t locate the driver.
At that time, there were no active warrants out for Latanowich, as his probation violation warrant had not yet been issued, said State Police spokesman David Procopio in an e-mail Friday night.
Yarmouth police have described Latanowich as a violent career criminal with a record dating back to an arrest for selling cocaine when he was 17. However, records reviewed Friday show that he was acquitted on repeated occasions after trials before a judge.
In 2010, Latanowich was sentenced on gun and drug charges to 4 to 5 years in state prison after reaching a plea agreement with prosecutors. He was released in 2013 on parole, which he violated just 25 days later. He was released again in June 2014.
He was also required to serve five years of probation after his release, which would have ended in November.
But court records show that Latanowich was arrested at least three times since his release from prison. He was charged with operating under the influence of alcohol in Fall River in 2014, and was sentenced to a year of probation for that charge.
He was also charged in October 2016 with allegedly strangling a pregnant woman and vandalizing her vehicle. That charge was dismissed after the victim refused to cooperate.
Two months later, he was arrested again after he allegedly stabbed a man who was stopped in a car at a traffic light in West Yarmouth. Court documents indicate a judge agreed to suppress evidence in the case, leading to its dismissal.
Separate court records show that Latanowich had violent relationships with at least two women, both of whom claimed to have children with him. In a restraining order filed in May 2007, a woman wrote that Latanowich “came to my residence and choked me by putting his hands over my mouth and nose while sitting on top of me screaming.”
”There is a long history of violence with him,” she wrote. “I truly believe that he is crazier than ever and put no limit on what he is capable of when he gets mad.”
Latanowich made similar allegations of violence against the woman later that year.
In October 2016, the pregnant woman Latanowich allegedly assaulted also sought a restraining order, writing in an affidavit that he “has a long history of violent crimes. He had choked me [threw] me on the ground and slashed my tire.”
She said she feared that “he might be released and I am fearful he will come to my house.”
On Friday afternoon, a section of Blueberry Lane was still closed to traffic, and the house was cordoned off.
In town, the grief over Gannon’s death mingled with outrage.
“Everyone that I’ve spoken to, they’re angry that this guy had so many prior arrests and he was still walking around,” said Philip Wallace, a town councilor. Gannon “was a fine young man in the prime of his life, and to have it taken away like that is just tragic.”Danny McDonald of the Globe staff contributed to this report. Milton Valencia can be reached at Milton.Valencia@globe.com. Follow him on Twitter @MiltonValencia