The 27-year old assailant, identified as Joseph "Sanish" Pallipurath, who drove all across the US from California to New Jersey to confront his 24-year old wife Reshma James, escaped after fatally shooting her.

Police said he was still potentially dangerous as he possessed the sliver handgun with which he shot the victim.

While Reshma died four hours later, the two others, identified as Dennis John Malloosseril, 23, and Silvy Perincheril, 47, were reportedly in "very critical condition". The hospital though declined to give any information.

Perincheril is Reshma's cousin and a mother of three.

The incident occurred towards the end of the three-hour Sunday service at the St Thomas Syrian Orthodox Kanaya Church in Clifton, when Pallipurath confronted his wife in the Church and shot her, along with another woman and a man.

Apparently apprehending trouble, Reshma had obtained a Court order restraining her husband from coming near her.

Police said she had suffered abuse right from the initial days of her marriage in Kerala, and after the couple moved to California, she continued to complain of abuse.

Recently, Reshma had left her husband to live with a relative in New Jersey.

About 200 people were inside the church at the time of the incident and police received several emergencies calls.

Several law enforcement agencies were involved in the search for the suspect who escaped in a jeep.

Clifton Mayor Jim Anzaldi said he heard about the shooting while attending Sunday service in a different church.

"It's a shock, that somebody would have gone into a church like that," he told the media. "It's a terrible thing."

A local newspaper Record quoted friends of Malloosseril, one of the victim, as saying he was near death and family members were making arrangements to donate his organs.

James had moved from India, where she had an arranged marriage, to California in January with her husband. But church members said the relationship soon turned violent.

"He was beating her," Record quoted Rev Thomas Abraham Lahayil, the church's vicar, as saying. "She had a restraining order against him."

She fled Sacramento in California where the couple had their home and moved in with her cousin Perincheril, who is the church's Sunday school teacher.

James has no immediate family in the US and her parents are en route from India, Church members were quoted as saying.

Malloosseril's aunt, Suja Alummoottil, told Record that she was in the vestibule with Perincheril and James when Pallipurath entered the building.

"He had a beard and was wearing a sweatshirt with the hood up," Alummoottil said.

"I knew something was wrong because who comes to church like that? He was angry and said 'I came to get my wife. I've been walking around without my wife for months.'" She then said the man said to his wife, "Are you coming with me?"

James asked Pallipurath not to make a commotion in the church, Alummoottil said, adding she never saw a gun.

Alummoottil said she went into the church's nave to find Perincheril's husband, when she heard the shots.