Three men and a woman, all members of the same family, were riding in a rickshaw traveling through Balochistan's capital city Quetta when armed men on motorcycles opened fire.
The rickshaw driver lived in Quetta, while his relatives were visiting from Sheikhupura District, Punjab Province, to celebrate Easter, Anjum told Morning Star News.
IG Moazzam Jan explained that the attack on the Christians, appeared to be a targeted attack. "It was a targeted attack and an act of terrorism", he continued.
ISIS said in a statement that its militants shot the Christians "with a pistol, which resulted in the killing of four of them, and all praise is due to Allah".
Pakistan's state religion is Islam, and around 97 percent of the population is Muslim.
Police said the casings of 9 mm bullets were recovered from the crime scene.
Christians celebrating Easter Sunday were attacked by a suicide bomber at an amusement park in Lahore in 2016, killing at least 69 people and wounding hundreds more. Dead bodies were shifted to Civil Hospital. The roads in between Christian communities and places of worship, however, remain vulnerable.
Christians have been targets of terrorist attacks and persecutions for blasphemy in recent years.
"Pervaiz Masih had been living in Quetta for 10 years".
The terror group has claimed responsibility but so far has not offered evidence of its involvement. A December 2017 attack on a Methodist church in Quetta killed eight.
Pakistan is ranked fifth on Christian support organization Open Doors' 2018 Word Watch List of the countries where it is most hard to be a Christian.