CHICAGO - The police officer was in full uniform, gathering evidence from a car break-in, when someone walked into the garage and shot him and the car's owner in the head, then fired another bullet into their heads as they lay on the ground.

The brazen, daylight slaying late last month of Officer Michael Flisk, 46, underscores what Chicago police have been saying for months: They are increasingly confronting people willing to attack them even as overall violent crime in Chicago continues to fall.

Five police officers have been killed in the line of duty this year - the most in at least 25 years. A sixth police officer was gunned down as he sat in his vehicle while off-duty just a few days before Flisk's death. In addition, reports of batteries on police officers have nearly tripled in a decade.

In 2009, there were just under 3,300 reports of battery on a police officer, more than twice as many as were reported in 2002 and nearly triple the number reported in 1999.

Police say the most dramatic jump came after the process of reporting the batteries was fully automated in 2004, when it became more accurate. But between 2007 and 2009, the number of reports climbed from 2,677 to 3,298 - a 23 percent increase - and this year, the number is on pace to climb well past 3,000 again.

"There is a lack of respect for the police, a lack of fear of the police that's getting worse," said Officer Nick Spencer, a 17-year department veteran. "They see a cop, and they just don't care anymore."

Police, activists, and even some former gang members point to other explanations, from the drop in the number of police officers on the streets to changes in the structure of gangs that have led to increased violence among the city's estimated 100,000 gang members.

Officers routinely return to their stations with stories about rocks and other debris pinging off their squad cars as they respond to calls or being confronted by crowds that no longer disperse just because an officer tells them to do so. Also, the sound of gunfire that used to stop whenever they arrived at a scene now continues long afterward.

Superintendent Jody Weis said there was "no indication whatsoever that there's any group of folks or gangs targeting our officers."

But he has said many times in the last several months that criminals are becoming increasingly brazen, and clearly he has been baffled in recent months by people who don't hesitate to take on a police officer.

"I simply cannot understand how a person can have such a total disregard of life and for those who keep order on the streets that he can attack, disarm, and then shoot and kill a uniformed officer in broad daylight," he said after the killing in July of Officer Thor Soderberg as he was walking out of a police station. "This savage act defies all human value."

It was a similar story when off-duty Officer Thomas Wortham IV was shot and killed when he tried to stop a group of men from stealing his motorcycle.

"He identified himself as a police officer, and they still killed him," Spencer said.

Another officer, Michael Bailey, was shot and killed while washing his car outside his home after returning from working the overnight shift.

The department has about 1,000 fewer officers than the 13,500 it had as recently as March 2008, according to the police union. As the department scrambles to cover the city - more officers are riding alone in squad cars, dubbed "rolling coffins" by beat cops - there is a growing concern that the uptick in violence is linked to the smaller force.

"The criminal element sees there are fewer police officers out there," said Lt. Robert Weisskopf, head of the Chicago police lieutenants' union. "Criminals go where there's no pressure on them . . . and the easier it is, the more bold they will become."

With Weis saying that more than half of the homicides committed in the city this year involved gangs, police say they have no doubt that many of the assaults and at least some of the police slayings were committed by gang members - including the 19-year-old parolee charged with killing Flisk.

"They feel like they can get away with a lot more," said Phil Cline, Weis' predecessor, who said he noticed during his tenure that gangs seemed to have less and less fear of police. "When you think of a 19-year-old gang banger murdering an officer processing a crime scene, it's unbelievable."