Officer Angela Ward never saw it coming. As the rookie cop entered a snow-swept bungalow this week, a murder suspect shot her in the head.

He then charged around the building and mowed down her two partners -- but not before they killed the terrified security guard running from the melee.

As guns boomed on all sides, innocent citizens were caught in the cross-fire.

"OK," said Lt. Joe Key, stepping into the fray and silencing the guns. "We got three dead police officers, one dead security guard and I don't know how many wounded bystanders. This is going to make one hell of a lawsuit."

His circle of students burst out laughing. Even in this simulated shootout, he told them, tensions run high and people make stupid mistakes. And cops are no different.

That message was repeated over and over Tuesday at the Baltimore Police Department's firing range in Gunpowder Falls State Park as 20 ordinary people with ordinary jobs gathered to learn about the pitfalls police officers face when they pull out their guns.

Secretaries, office clerks and computer operators -- many of them from tough neighborhoods where police often are regarded with suspicion -- got to play cops for a day. And none walked away unchanged.

"I have to be honest," said Paulette Medley, 42, of West Baltimore. "I came here expecting them to tell us how cops are never wrong, but that's not how it was. You understand for the first time how police officers get killed and innocent people get shot.

"You see that the officer is a person just like you, who's scared just like you."

In a city where nine suspects were killed by police last year and 15 more were wounded, it's a real-life lesson. And training officers hammer it home inside and outside the classroom during the monthly seminars with examples drawn from actual cases that show how appearances aren't always what they seem.

As they shifted in their chairs and cringed, the civilians watched videotapes of officers getting shot with their own guns, stabbed and beaten by suspects they had underestimated.

And they listened as Lieutenant Key -- a founding member of the department's SWAT team and supervisor of the firing range -- described scenarios that have taught Baltimore police some of their hardest lessons. Later, he sent his class out into the cold with guns on their hips to learn for themselves.

"Now I know why police shoot people 17 times," said Ms. Ward, 31, a postal worker who was the first to get shot in the simulated bungalow gunbattle. "I was so scared, I just kept on pulling the trigger until all my bullets were gone."

Such was the case last August when Officer Harold Carey shot Michael R. Goodman 14 times in a Northwest Baltimore movie theater when the man aimed what appeared to be a .357-caliber Magnum revolver at him.

An autopsy revealed that Mr. Goodman was high on cocaine. The weapon turned out to be a pellet gun. A department investigation found that the officer fired in self-defense.

"He had no idea he was dealing with a pea-shooter, and he did exactly what he was supposed to do," said Lieutenant Key, who reviews all police shootings to look for ways of improving training. "He ordered the guy to drop the gun and, when the guy pointed it at him, the officer shot him -- over and over again -- until he finally went down and let go of it."

Officer Carey's hands were shaking so badly that he jerked the trigger as he fired, Lieutenant Key said, and almost all of his shots hit below the waist.

In contrast, the lieutenant was not spare in his criticism of Officer Edward T. Gorwell II for killing 14-year-old Simmont Thomas last April. The teen-ager was among a group of unarmed boys who bailed out of a stolen car with Officer Gorwell in pursuit. As they ran across a West Baltimore park at night, the officer shot the youth in the back.

Officer Gorwell, who has been suspended since the shooting, justified his actions by saying he had heard a sharp cracking sound in the dark that he thought was a gunshot and fired in the direction of the noise. He was charged with manslaughter, but the case was dropped when a juror skipped out during trial.

"If Baltimore police officers were allowed to shoot at every sound they hear in the dark, we'd have a lot of innocent dead people in the streets," said Lieutenant Key, who testified at the trial. "It was a gross violation of his training and department procedures -- plain and simple."

But, even when they follow the rules, he said, good officers can get killed.

In 1985, Officer Vincent Adolfo was shot to death as he attempted to search a car theft suspect in an East Baltimore alley. Flint Gregory Hunt was standing spread-eagle against a wall when he spun around and bowled the officer over. Hunt then drew a .357 Magnum from his belt and shot the officer twice.

Hunt received a death sentence and the slaying prompted changes in department procedures on searches, Lieutenant Key said.

"Now, we teach them to make all suspects lie face-down on the ground with their arms extended and their palms turned up before they go anywhere near them," Lieutenant Key said. "What might appear to be terribly demeaning to a person is actually designed to protect him and the officer.

"Do they always do it that way? No. Does it drive me crazy? Yes."

Responding to a call in 1992 that a man with an ice pick was threatening people in a house in West Baltimore, Officer Ira Weiner walked in through the front door before other officers arrived to help him. High on cocaine, Lewis Thomas rushed the officer and stabbed him repeatedly, then grabbed his service weapon and shot him.

Moments later, Thomas was killed by officers arriving at the scene.

"He was a dedicated cop, a gung-ho guy," said Lieutenant Key. "And he underestimated the situation. He wanted to do the best job he possibly could, and he left himself vulnerable to that one-in-a-million lunatic."

The discussion was more than academic for Officer Carl Trogdon, an instructor standing in the back of the room who was shot just below his right knee in 1990 by a drug suspect packing two guns. His partner grabbed Edward Ramos after seeing a cocaine sale, then took a pistol from the small of the suspect's back.

"All the sudden, the guy got hinky and pulled away from us," Officer Trogdon said. "He came out with another gun from the front of his pants and started shooting. He wounded two of us. God was definitely looking down on me that night."

Ramos is now serving a 105-year prison sentence for attempted murder in the shooting, Officer Trogdon said.

"I've been Monday morning quarterbacking that night ever since," he said. "What could I have done differently? How could I have prevented it from happening? It still makes me nervous first thing in the morning when I'm down on the firing line and the first shot goes off."

Ms. Ward knows the feeling after her simulated brush with death outside the bungalow.

"It all happened so fast," she said.