Maine law enforcement officers are firing their weapons more frequently in the line of duty.

In November alone, there were four officer-involved shootings in Maine, including Tuesday’s fatal shooting of a sheriff’s department dispatcher who had just gunned down a maintenance worker in Dover-Foxcroft.

For the year, police have been involved in nine shootings in the state. That compares with an average of three a year during the 1990s and an average of five a year in the 2000s. This year’s shootings caused six deaths and three injuries.

Officer-involved shootings have increased because police are facing more threats than ever, said Robert Schwartz, executive director of the Maine Chiefs of Police Association.

There are more guns and knives, more drugs, more mentally ill people on the street and more people acting aggressively toward police, he said.

“I think law enforcement, more than anyone, would like to find a way so this doesn’t happen,” said Schwartz, who served on Maine police departments for 30 years. “No one wants to shoot at anybody, and no one wants to get shot themselves. That’s the bottom line.”

The increase in police shootings comes even with the crime rate low. Maine had the lowest violent-crime rate nationally in 2010, FBI statistics show.

Statistics from the Attorney General’s Office show there were 30 police-involved shooting in the 1990s — not a single one in 1995. There were 51 shootings from 2000-09.

In the first two years of this decade, there have been a total of 14 police shootings. The Attorney General’s Office declined to comment on the increase.

This year’s shootings have occurred across much of the state, involving the York County and Androscoggin County sheriffs’ departments, Maine State Police, the Maine Warden Service, and police departments in Kennebunk, Portland, Belfast, Lewiston and Farmington.

Being a police officer is inherently dangerous, said Portland’s acting police chief, Michael Sauschuck. Nationally, 56 law enforcement officers were killed last year in the line of duty and nearly 54,000 officers were assaulted. No Maine officers have been killed in the line of duty this year.

In recent years, Portland police have gotten more calls for service overall and have arrested more people for weapons violations, Sauschuck said. Also, criminals are more likely now than years ago to be antagonistic and come at officers aggressively, he said.

“There’s undoubtedly been an increase in the disrespect level overall,” he said.

There’s no national database on the numbers of shootings in which police fire their weapons at somebody, said Charles Miller, who heads the Law Enforcement Officers Killed and Assaulted program for the FBI.

But he said it wouldn’t surprise him if the numbers were rising. The number of unprovoked attacks on police has risen 150 percent since 1980, he said, and it stands to reason that police would defend themselves.