(CNN) -- An FBI tactical team forced its way into the abandoned, debris-strewn shell of the Glory Days tavern in Herkimer, New York, early Thursday and killed the man who police say fatally shot four people a day earlier.
An FBI dog died, but no officers were wounded in the firefight that left Kurt R. Myers, 64, dead, police said.
Myers' death left many questions unanswered, including why the apparent loner with no significant criminal record shot six people, killing four and leaving the other two in critical condition, State Police Superintendent Joseph D'Amico told reporters.
"We think they were unprovoked and random," he said of the attacks.
In addition to the shootings in Herkimer County, about 70 miles west-northwest of the state capital, Albany, a federal law enforcement source briefed on the investigation said Myers also is believed to have blown up his house.
After the shootings Myers went to the abandoned bar, which D'Amico said was strewn with debris.
During a 12-hour standoff with police, he may have hidden inside a small room to shield himself from tear gas lobbed into the building by police.
The FBI tactical team, led by a police dog, moved on Myers shortly before 8 a.m. Thursday, D'Amico said.
Myers first fired on them through the closed door, then again into the doorway as agents stormed the room, he said.
The dog, a German shepherd, died in the firefight.
"As unfortunate as it was that the canine lost his life, it could just as easily have been an officer," D'Amico said.
The string of incidents began Wednesday morning. Authorities first received a report of a fire at a residence at 9:29 a.m., D'Amico said. The call was followed minutes later with reports of shootings at a barber shop and at an oil change business in Herkimer, authorities said.
Police believe Myers spoke to some people at the barber shop before firing repeatedly, D'Amico said.
Harry Montgomery, 68, and Michael Rancier, 57, were pronounced dead at the scene. Two other people were in critical condition at St. Elizabeth Medical Center in Utica.
At the oil-change business, employee Thomas Stefka and Michael Renshaw, a 20-year veteran of the State Department of Corrections, died.
Authorities have no information about personal problems or mental issues that could have contributed to the attack, D'Amico said, and know of no connection between Myers and the victims.
A 1973 drunken driving arrest is the only previous incident on Myers' record, D'Amico told reporters.
New York Gov. Andrew Cuomo went to Herkimer on Wednesday, saying he wanted to make sure the state was providing as many resources as possible in the investigation. Reporters pressed him about New York's new gun-control laws, which were the first in the nation to be enacted after the Newtown, Connecticut, school massacre.
The laws fortified New York's existing assault weapons ban, limited the number of bullets allowed in magazines and strengthened rules that govern the mentally ill, which included a requirement to report potentially harmful behavior.
Cuomo said he would discuss the laws later.
"Gun violence has been with us for a long, long time," the governor said. "I think the challenge for government, the challenge for society, is to do the best that it can."
CNN's Jason Kessler, Eden Pontz, Leigh Remizowski and Emily Minner contributed to this report.