Police told CNN Sunday that Aqsa Shakeel, 26, and her husband, Muhammad Shakeel, 30, were visited by a group of relatives on Wednesday at their home in Thikriwala, a village in Pakistan's eastern Punjab province.
Police said a heated argument broke out between the couple and the family members, who included Aqsa's brother, named as Muhammad Mauvia, and her mother, Majeeda Bibi.
Aqsa's family disapproved of the marriage, according to police, though no further details were given.
A search for the couple was initiated when the husband's father, Muhammad Kushi, reported the couple missing later Wednesday. Their bodies were discovered in a canal near the village Thursday evening. An autopsy report revealed that they had been tortured and shot in the head.
Police said only one relative, identified as M Khawar, has so far been arrested in connection with what police are treating as a murder case. The other relatives, including Aqsa's mother, brother and an uncle, remain at large.
Aqsa, a healthcare worker, had been married to Muhammad, who worked in a government school, for four years.
Surge of 'honor killings'
The killings are the latest in a recent surge of so-called "honor killings" in Pakistan.
Earlier this month, another pregnant woman was killed
by her family in eastern Pakistan because she married against family members' wishes three years ago, according to police.
Muqaddas Tawfeeq, who was eight months pregnant, was visiting a maternity clinic for a checkup when her mother appeared and "dragged her away" to her maternal home, her husband told CNN. Once there she was attacked by her brother, who slit her throat, police said.
And in another incident in Pakistan within days of that attack, a man beat his teenage sister to death
with a large wooden stick, reportedly because he didn't want her to marry her boyfriend.
The victim's father, Yousuf Masih, said they were against the match because the two families were related.
"They started arguing," he said of his daughter and son. "He hit her with the stick, he has no intention to kill her. Things just got out of hand, he reacted in anger. In the end, I guess it did become an issue of honor."
Violence against women is rampant in Pakistan, according to the independent Human Rights Commission of Pakistan
It said that in the first five months of 2016, as many as 212 women were killed in the name of "honor." In a case earlier this month, a Pakistani teen was burned to death
by her mother and brother for eloping against their wishes.
The crimes originate from tribal and cultural practices and are often meted out as punishment for behavior viewed as bringing dishonor to a family or village.
Honor killings in Pakistan's Christian community, which the Masih family belongs to, are "extremely rare," said Peter Jacob, a minority rights activist and secretary at the National Commission for Justice and Peace.