NEW YORK (Reuters) - A gunman who spent 17 years in prison for murder ambushed and killed two volunteer firefighters and wounded two others on Monday near Rochester, New York, as they responded to a house fire he deliberately set, police said.

William Spangler, 62, shot and killed himself after a gunfight with a police officer in Webster, a Rochester suburb, Webster Police Chief Gerald Pickering said.

"It was a trap set by Mr. Spangler, who laid in wait and shot first responders," Pickering told a news conference.

Separately, a police officer in Wisconsin and another in Texas were shot and killed on Monday, according to police and media reports.

The attacks on first responders came 10 days after one of the worst mass shootings in U.S. history that left 20 students and six adults dead at an elementary school in Newtown, Connecticut and intensified the debate about gun control in the United States.

Spangler was convicted of manslaughter in 1981 for beating his 92-year-old grandmother to death with a hammer, according to New York State Department of Corrections records, and after prison he spent eight years on parole.

"We don't have an easy reason" for the attack on the firefighters, Pickering said, "but just looking at the history ... obviously this was an individual with a lot of problems."

Spangler opened fire around 5:45 a.m. after two of the firefighters arrived at the house in a fire truck and two others responded in their own cars, Pickering said.

Pickering appeared to wipe tears from his eyes at a news conference earlier on Monday when he identified the dead firefighters as Lieutenant Michael Chiapperini and Tomasz Kaczowka. Chiapperini was also a police lieutenant.

The injured firefighters, one of whom was in critical condition, were identified as Joseph Hofsetter and Theodore Scardino. Off-duty Police Officer John Ritter was hit by gunfire as he drove past the scene.

Pickering said police had found several types of weapons, including a rifle used to shoot the firefighters. As a convicted felon it was illegal for Spangler to own guns.

Police had not had any contact with Spangler in the "recent past," Pickering said.

Four houses were destroyed by the fire and four were damaged, Pickering said.

COPS TARGETED

Police Officer Jennifer Sebena, 30, was found dead on Monday in the Milwaukee, Wisconsin, suburb of Wauwatosa, police said.

Sebena was on patrol between 3 a.m. and 5 a.m. and wearing body armor when she was shot several times, police said. She was found by another officer after she did not respond to calls from the police dispatcher.

In Houston, Texas, an officer with the Bellaire Police Department died after a shootout at around 9 a.m. and a bystander was also killed, according to local media reports.

A spokesperson for the Houston Police Department was not immediately available for comment. A police officer answering the telephone confirmed media reports but declined further comment. A suspect was in the hospital, according to reports.

Before Monday's killings, the Washington-based National Law Enforcement Officers Memorial Fund reported that 125 federal, state and local officers had died in the line of duty this year.

Forty-seven deaths were firearms-related, 50 were from traffic-related incidents, and 28 were from other causes, it said.

How could they release someone who beat his grandmother to death with a hammer? I thought murder penalty is life imprisonment. :/

I wonder how these maniacs derive joy killing other people.