A man killed seven people in New Jersey and Pennsylvania over a seven-week period during shooting rampages in which at least some victims may have been targeted at random, authorities said Thursday.

The killings began in Elizabeth, New Jersey, in mid-May and ended 70 miles away in Pennsylvania on Sunday, when three people were shot in the middle of the night, two as they sat in a car.

Todd West, 22, of Elizabeth, was arrested Monday by police in Allentown, Pennsylvania, who spotted him and an accomplice who matched the descriptions of two men wanted for robberies earlier in the day, prosecutors said.

The police work "may have prevented more people from being killed, potentially, because it’s pretty apparent that these guys meant business," said Terry Houck, first district attorney in Pennsylvania’s Northampton County, where one of the killings occurred.

West faces charges including seven counts of homicide and one count of attempted murder. It was unclear if he had hired a lawyer, and a call to an attorney who previously represented him went unanswered Thursday.

Prosecutors said his first victim was a cousin, killed in an apartment building in Elizabeth on May 18. Three other victims were killed June 25 in Elizabeth.

Prosecutor Grace Park in Union County, New Jersey, called the killings a "horrific event." Her office said a motive was unclear; there was no evidence that drugs, gang activity or robbery played a role.

Houck said no connection had been found among the victims in the two states.

"Nothing other than random at this point," Houck said.

Authorities said they did not know much about West’s background. New Jersey court records show he pleaded guilty to theft in 2012 and was found guilty of a drug charge in 2013.

Police and prosecutors in the two states gave the following account of the shootings:

On June 25 in Elizabeth, he killed Dennis Vega, 28, of Elizabeth, early in the morning. Vega was found lying on the ground dying of gunshot wounds. Late that night, he fatally shot Jamil Payne, 29, and then about an hour later, Kelvin Nelson, 32. They were found about a mile apart.

Shortly after Nelson was reported attacked, police responded to another shooting by West. That victim was expected to survive.

The same .38-caliber revolver was used in all four shootings.

On Sunday, West confessed to killing three people during the middle of the night in eastern Pennsylvania.

Kory Ketrow, 22, was fatally shot shortly after 3 a.m. in Easton as he was walking home from a friend’s house.

Less than an hour later, Francine Ramos, 32, was found dead of gunshot wounds in the driver’s seat of a car in Allentown. Trevor Davante Hall Gray, 21, appeared to stagger away and was found leaning against a nearby parked car with gunshot wounds. He died a short time later.

Allentown police said West confessed to the killings in Allentown and Easton.

West identified an Easton man as having purchased the ammunition used in the Pennsylvania shootings and a Newark man as the person who drove him to both crime scenes. Both were charged in connection with the killings.

Surveillance video was recovered showing the purchase of the ammunition at a Wal-Mart in Easton at about 2:45 a.m. Sunday, police said.

West also confessed to shooting at the back of a car in Easton after the killing there, police said. The occupants of the car were not injured.

West was scheduled to appear in court Monday in Allentown.

Catalini reported from Trenton, New Jersey, and Sisak reported from Philadelphia.