PHOENIX -- Funeral services were held Monday for slain Phoenix police Officer Nick Erfle, and Gov. Janet Napolitano ordered all flags at state buildings be flown at half-staff in his honor.

IMAGES: Service, Erfle's Life

The funeral began at 10 a.m. at Phoenix First Assembly Church. Burial followed the funeral and took place at Phoenix Memorial Park.

Erfle, 33, was an eight-year veteran of the Phoenix Police Department. Married and the father of two, he was shot and killed Tuesday after he and his partner stopped a jaywalker in central Phoenix.

"Every officer who was lucky enough to know Nick paints a picture of Nick that will not fade with time," Phoenix Mayor Phil Gordon said at the funeral. "He brought enough electricity to light the entire precinct."

Erfle's widow, Julie, wrote a letter which was read by her sister. In it, she described the pain she felt for their two sons, ages 5 and 3.

"I do not mourn for his life, but mourn for my own. Mostly I mourn for all the memories our sons never had a chance to make," the letter read.

Visitation for Erfle was held Sunday at Unitarian Universalist Congregation of Phoenix in Paradise Valley.

Colleagues: Erfle Inspired Force

Colleagues have been honoring the memory of the slain Phoenix officer with stories and reminiscences.

Sgt. Phil Roberts said Erfle was one of the most-liked officers and an inspiration to the force. "He was a fighter," Roberts said.

"He fought through two bouts of cancer. The second bout was very serious," Roberts said.

After taking time off for treatment, Erfle returned to uniform patrol as quickly as he could.

"He was very eager to get back to work," said Phoenix police Sgt. Joel Tranter. "At the first opportunity he requested to get back into a uniform and get back on the streets. Police work was a passion of his."

Tranter said Erfle's partner, Rob Rodarme, who was there when Erfle was shot, went to the police academy with Erfle and that the two were close.

"He's absolutely traumatized, devastated," Tranter said. He said Rodarme is taking time off to recover from the trauma.

Officer Jeffrey Meyers said Erfle enjoyed fantasy football.

"That was one of the things he really enjoyed outside of work," Meyers said.

Meyers said he's coping with disbelief.

"When Nick was working with our squad, when riding with him, once he had his muffin in the morning, it was time to go find the bad guys," Meyers said.

Officer: Job Is 'Never Routine'

Officer Dominic Cano said Nick was a friend.

"A great friend. A great father. He cared a lot about the people he worked with," Cano said.

"No matter what Nick did, he did it to the best of his ability. He was an exceptional officer. He really was," Cano said.

Cano said officers never know what they're going to wake up to.

"They call it a routine stop or job, but it's never routine. You never know what is going to happen," Cano said.

Sgt. Rodrigo Hernandez said he'll remember Erfle's dedication to duty.

"He told me he did it because he cared about his community. He wanted to make a difference," Hernandez said.

Hernandez said it's a difficult time for the force.

"When you work with people of this caliber, we come together. We surround each other with love and support," he said.

ICE: Shooter Was Illegal Immigrant

The man who shot and killed Erfle before being fatally shot by authorities was an illegal immigrant, a federal official said.

Erik Jovani Martinez, 22, was in the country illegally last year when he was arrested and convicted on theft charges, said Vinnie Picard, a spokesman for Immigration and Customs Enforcement.

He said Martinez was deported on March 3 last year, and at some point re-entered the country illegally.

CBS 5 investigated the shooter's records and found that Martinez was born in Mexico and came to the U.S. with his parents as an infant.

He joined a gang at age 13. Before his conviction, a presentence investigation determined he was a medium risk to re-offend, even with an extensive juvenile history.

Lt. Benny Pina said a bench warrant issued against Martinez in January stemmed from a June 2006 assault against his girlfriend involving a shotgun. A detective working on the case was unable to locate Martinez, a member of a street gang, to arrest him.

Martinez's former fiancee, Rubi Salazar, told CBS 5 Martinez beat her almost to death, killing their unborn child.

Makeshift Memorial Grows

Since Tuesday, Erfle's friends and fellow officers, as well as people who never knew him, have stopped by a makeshift memorial at 24th Street and Thomas Road to leave notes, flowers, candles and stuffed animals.

One person left a Purple Heart with a note to Erfle's family that said, "I knew him, yet I didn't know him. I know them all."

The memorial has become a gathering place for fellow officers to mourn their loss. At least a dozen officers, some of whom worked closely with Erfle, gathered at the memorial Wednesday to read the notes left behind.

One officer left a picture of Erfle taken last year with his fellow officers.

Residents visited the memorial to leave gifts and pray.

Old and young, officer and civilian, every person who has visited the memorial has been moved and saddened by the loss of another Phoenix police officer.