LAWRENCE — Roberto Plaza had a habit of visiting a yellow house on Hampshire Street known to harbor drug dealers, said his sister, Jacqueline Plaza.

And when he was shot in the chest and killed Sunday night he had apparently been trying to buy Seroquel pills to help him sleep, said Ericka Gaznick, his former girlfriend and the mother of his 10-year-old daughter.

Plaza, 32, of 218 Bruce St., became the city's fourth homicide victim so far this year in what police Chief John Romero called a "drug deal gone bad."

Luis Serrano, building superintendent at the nearby Rita Hall assisted-living complex, said that about 9:30 p.m., he heard a loud gunshot near Santo Domingo Liquors, about two blocks south of the apartment complex at 490 Hampshire St.

"I didn't pay no mind," said Serrano. "You hear that all the time."

But he did pay attention when, soon after, he heard screeching tires followed by a loud crash just outside the building.

"I looked out the window and saw the car had crashed into our parking lot," Serrano said.

He grabbed his flashlight and went outside, where a crowd of neighbors had gathered around the vehicle. He looked inside the car and saw a man with what appeared to be a gunshot wound to the chest.

"He was out," Serrano said.

Plaza was declared dead at Lawrence General Hospital.

According to police, Plaza was shot in the chest, and then his car careened down the road and slammed into the chain-link fence in front of Rita Hall, damaging two other cars and scattering debris around the sidewalk and parking lot.

At first, police thought it was a routine accident, until they saw the wound.

Plaza lived with his mother and father. Originally from Puerto Rico, Plaza has a 4-year-old child there as well as the 10-year-old daughter, who lives with Gaznick in Lowell.

Marilin Cancel, another sister of Plaza, who lives on Monmouth Street, said the last time she talked to her brother he had asked to borrow $20. She gave the money to her father to give to Plaza.

"He told my father he was going to get two pills," said Cancel. "There was some guy on Hampshire Street selling them. They were for sleeping."

According to various Web sites, Seroquel is prescribed to treat anxiety disorders and insomnia, among other ailments, but is highly addictive. One Web site states that it has become popular among jail inmates.

Jacqueline Plaza said her brother frequented a yellow house on Hampshire Street that always had people "going in and out."

She said she and others have called police many times to complain about drug houses in the neighborhood.

A small crowd of family and friends gathered outside the 218 Bruce St. two-family house yesterday morning, comforting one another and talking about Plaza.

Some said that despite a criminal past, he was doing things trying to straighten out.

Gaznick said Plaza had been working at her father's HVAC company in Haverhill, and that he saw his daughter every weekend.

Gaznick pointed to rose bushes her former boyfriend planted Sunday, near a colored chalk drawing of a monkey's face he had made on the sidewalk near the driveway while playing with his nieces and nephews over the weekend.

"He was straightening his life out," she said. "He'd had some problems in the past. But he was doing good."

According to court records, Plaza had at least five cases filed against him in Lawrence District Court, including assault and battery, intimidation of a witness, assault and battery on a police officer, and indecent assault on a person over the age of 14. While he was never sentenced to jail, he did spend time behind bars while being held without bail over the course of several cases, according to the District Court.

In March 2007, Plaza was caught breaking into cars in the Bruce Street area, according to a story in The Eagle-Tribune. He was charged with malicious destruction of property, disorderly conduct, assault and battery on a police officer, resisting arrest and illegal possession of burglarious tools.