The gunman who went on a shooting rampage at his South Florida apartment building, killing six people, was a lonely man who spoke about having pent up anger, those who knew him said Sunday.

Pedro Vargas, 42, lived on the fourth floor of a barren, concrete apartment complex in the Miami suburb of Hialeah with his elderly mother. He rarely spoke with others there, and confided to a man who worked out at the same gym that he liked to work out his anger by lifting weights and trying to get big.

"He'd just say this was the only thing that would keep him normal, pulling out all the anger in the gym," Jorge Bagos told The Associated Press.

Bagos said the gunman expressed frustration over bad experiences with women and losing all his hair from using steroids.

On Friday night, Vargas set a combustible liquid on fire in his apartment, sending the unit into flames, police said. Building manager Italo Pisciotti and his wife went running toward the smoke. Vargas opened his door and shot and killed both of them, Lt. Carl Zogby, a spokesman with the Hialeah Police Department said.

Vargas then went back into his apartment and began firing from his balcony. One of the shots struck and killed Carlos Javier Gavilanes, 33, who neighbors said was returning home from his son's boxing practice.

Vargas then stormed into a third-story apartment, where he shot and killed a family of three: Patricio Simono, 64, Merly Niebles, 51, and her 17-year-old daughter.

For eight hours, police followed and exchanged gunfire with Vargas throughout the five-story apartment complex as terrified residents took cover in bathrooms and huddled with relatives, sometimes so close to the gunfire they could feel the shots. In the final hours, Vargas took two people captive in a fifth-story unit. Police attempted to negotiate with him, but the talks fell apart and a SWAT team swarmed in, killing Vargas and rescuing both hostages.

On Sunday, neighbors struggled to remember anything more than cursory exchanges with Vargas. He was often seen taking his mother, who used a walker, to run errands and go to doctor appointments. Sometimes, he greeted residents and politely held open doors. Other times, he could be noticeably anti-social.

One woman recalled how she would see him wait for the elevator, only to then take the stairs if he saw someone was inside when it arrived. And neighbors never saw him with anyone other than his mother.

"He looked very alone," said Isael Sarmiento, 42, who lived on the same floor as Vargas, across an open, gray and red concrete terrace. "I saw it in his face sometimes, like he was someone who had spent many years alone."

Nearly every morning, Vargas would get dressed in gym shorts and a tank top and drive to an L.A. Fitness gym, water bottle in hand, neighbors said.

"He looked like an athlete," said Consuela Fernandez.

When shown Vargas' photo, many of the men working out at the gym recalled seeing him there, doing pull ups and lifting weights for hours at a time. Bagos said Vargas worked out almost religiously, and always alone.

"Sometimes it looked like he was in his own world," Bagos said.

Vargas didn't talk much, but occasionally he would share hints of the frustrations he described taking out at the gym.

"He said he'd rather be by himself, that women were no good," Bagos said.

Vargas also described how he was dieting and wanted six-pack abs. He was tall and relatively muscular, but when Bagos suggested Vargas get a tan so that his muscles would look better, he scoffed.

"I don't like the heat," Bagos remembered Vargas saying. "The heat makes me mad."

Lately, Vargas seemed to keep even more to himself. When Bagos tried saying hello, Vargas would turn and walk in the other direction.

"I thought he was going through problems and I kept away from him," he said.

Police said Vargas had no known criminal history, and they'd never responded any calls from the home. His past, they said, was "unremarkable."

"Nobody seems to know why he acted the way he acted," Zogby said.

On Sunday, residents stayed away from the building or kept inside their apartments. A few lingered in the stairways, staring from time to time at Vargas' apartment. The front door was half burnt and a black mix of water and ash from the blaze was scattered along the walkway.

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