In January 1976, he moved into a two-family home in Yonkers, a suburb of New York. Berkowitz became convinced that the German shepherd that lived in the house and other neighborhood dogs were possessed by demons who ordered him to murder attractive young women. One of the neighborhood dogs was shot during this time, probably by Berkowitz. He also began to see his neighbors as demons. In April, Berkowitz moved to an apartment house in Yonkers, but his new home also had dogs. His neighbor, retiree Sam Carr, had a black Labrador retriever named Harvey, who Berkowitz believed pleaded with him to kill. He also saw Sam Carr as a powerful demon and was referring to him when he later called himself Son of Sam. On July 28, 1976, Berkowitz quit his job as a security guard. Early the next morning, he walked up to a parked car in the Bronx where two young women were talking and fired five bullets from his.44 revolver into the vehicle. Eighteen-year-old brunette Donna Lauria was killed instantly, and her friend Jody Valenti was wounded. Police could find no motives or leads in the shooting.
In the early morning of October 24, Berkowitz struck again, critically wounding 20-year-old Carl Denaro as he sat in a car and talked with a female friend in Queens. A little more than a month later, on November 26, 16-year-old Donna DeMasi and 18-year-old Joanne Lomino were shot and seriously wounded in the street on their way home from a movie. On January 30, 1977, Berkowitz fatally shot Christine Freund as she sat in a car in Queens with her fiancée. Police began to suspect that these crimes were perpetrated by a single killer, but few bullets were found intact to confirm the assumption. On March 8, 19-year-old college student Virginia Voskerichian was shot to death as she walked home in Manhattan. A bullet was found intact, and it matched a bullet found at the scene of Berkowitz's first murder. The New York police announced that a serial killer was on the loose, known to be a white male in his 20s, with black hair and of average height and build. A large group of detectives was organized--the "Omega" task force--to track the killer down. On April 17, 18-year-old Valentina Suriani and 20-year-old Alexander Esau were shot and killed by the same gun as they kissed in their parked car near the Hutchinson River Parkway. This time, the .44-caliber killer left a note in which he referred to himself as the Son of Sam.
On April 29, Berkowitz shot Sam Carr's Labrador retriever. He had previously sent an anonymous, threatening letter to Mr. Carr concerning the animal. The dog recovered, and the Yonkers police began an investigation. Meanwhile, Berkowitz began sending bizarre letters to other neighbors and his former landlords. These individuals began to suspect Berkowitz to be the Son of Sam and reported their suspicions to local police. The Omega task force was subsequently notified, but the detectives had received thousands of reports of Son of Sam "suspects" and were having a difficult time sifting through all the dead-end leads. On June 26, the Son of Sam struck again, wounding Judy Placido and Sal Lupo as they sat in their car after leaving a Queens disco. Public concern over the rampaging serial killer grew to panic proportions, and New York nightclubs and restaurants saw a dramatic drop in business. A blistering heat wave and a 25-hour blackout in mid-July only increased the tension. On July 31, just two days after the anniversary of his first killing, Berkowitz shot a young couple kissing in a parked car in Brooklyn. Twenty-year-old Stacy Moskowitz was fatally wounded, and her boyfriend, Bobby Violante, lost his left eye and nearly all the vision in his right eye.
A few days later, a major break in the case came when an eyewitness came forward to report that she had seen a man with what looked like a gun minutes before the shots were fired in Brooklyn. Her information led to the first police sketch of Berkowitz. More important, she reminded investigators that two police officers had been writing parking tickets on her street that night. A search of tickets issued eventually turned up Berkowitz's car. At the same time, Yonkers police investigated Berkowitz after he escalated a harassment campaign against one of his neighbors. Convinced he was the Son of Sam, they informed the Omega task force of their findings. The Omega detectives finally put two and two together, and on August 10 David Berkowitz was arrested while leaving his Yonkers home. He gleefully admitted to being the Son of Sam. On his person was a semiautomatic rifle, and he explained he was on his way to commit another murder. The .44-caliber revolver was also recovered. There was some question about whether Berkowitz was mentally fit to stand trial, but on May 8, 1978, he withdrew an insanity defense and pleaded guilty to the six .44-caliber murders. He was given six 25-years-to-life sentences for the crime, the maximum penalty allowed at the time. He has since been denied parole. Since 1987, he has been held at the Sullivan Correctional Facility in upstate New York, where he allegedly converted to Christianity.