MAPLEWOOD, Mo. -- A rookie firefighter was killed and two police officers were wounded when a gunman opened fire in Maplewood early today.

The dead firefighter has been identified as Ryan Hummert, 22, the son of a former Maplewood mayor.

Hummert was fatally shot as he got out of a Maplewood fire truck that came to fight a vehicle fire about 5:45 a.m. Monday. The gunman -- believed to be hiding in a home on Zephyr -- then shot two Maplewood police officers.

One of those Maplewood cops was critically wounded. The bullet apparently struck the officer's badge, which may have saved his life, a hospital spokeswoman said. A second Maplewood police officer was shot in the right shoulder. He is being treated, but his condition was unavailable.

At 10:10 a.m., the American flag and a Maplewood city flag were both lowered to half staff outside Maplewood City Hall.

At an 11 a.m. press conference, Maplewood Fire Chief Terry Merrell said, while fighting back tears: "We've lost Ryan in the line of duty doing what he loved. He will be missed."

Hummert was a firefighter-paramedic with Maplewood. He has been with the city since last August, when he graduated paramedic school. He graduated from the St. Louis County fire academy this year. Hummert graduated Rockwood Summit High School in 2004 and was the son of the former mayor of Maplewood, Andy Hummert, and Jackie Hummert.

It all started unfolding before 6 a.m. Monday, when firefighters were responding to a vehicle fire on Zephyr Place.

"They were about to put out the fire, then I heard a couple of shots," said one witness, Sanyog Rai, working at a 7-11 store on Big Bend. "I saw a cop holding his shoulder, and he fell down to the ground."

The house fire started shortly after that. Officers surrounded the home, believing the gunman was inside. Authorities weren't saying what sparked the gunman's rage.

Three hours later, dozens of police cars from a mix of area departments were still there. Many of the officers are crouching behind police cars with their weapons drawn. The St. Louis County police explosives unit rolled up after 9 a.m., as did an armored vehicle from the U.S. Marine Corps. FBI agents were suiting up in tactical gear. About 10:15 a.m., large puffs of black smoke billowed from the house on Zephyr.

Paul Kieselhorst, who lives about three blocks from the incident, said he heard four shots as his wife was leaving for work. Then, he heard a fifth shot. Kieselhorst saw an ambulance racing from the scene with lights and sirens blaring. He said police tactical units have evacuated a few people from adjacent homes.

"They still have the shooter holed up and people are at risk," Kieselhorst said.

The manager of the 7-11, Anuj Srivastava, was at home asleep when the shooting happened. His second-floor apartment is across the street from the convenience store. He watched the explosion from the truck fire.

"When the truck exploded, I saw the fireball coming up over the house 150 feet up," he said.

Casey Smith, who lives in the 7300 block of Zephyr Place, could hear helicopters hovering overhead about 8:45 a.m. today. She said she was virtually trapped in her home.

"A friend called to make sure I'm OK," Smith said. "I'm not going outside. Usually, this is a quiet place. I've never felt threatened."

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Nancy Cambria, Robert Cohen and Christian Gooden of the Post-Dispatch staff contributed to this report.