Los Angeles ( CNN ) Romel David is terrified . He and his family ca n't sleep , and they ca n't stop thinking about what will happen in Syria , thousands of miles away from the comfort of their California home . David said his brother-in-law , who emigrated to the United States about four years ago with his wife and two daughters , has been abducted by ISIS in Syria along with several other members of the family he had hoped to bring to the United States to get them out of harm 's way . David said his brother-in-law decided to return to Syria two years ago to be with them as they went through the process of applying for visas to the United States . The 59-year-old and 11 other family members were among the people taken by ISIS , which has targeted Assyrian villages in Syria this week . `` We anticipate the unthinkable . It 's absolutely devastating , '' David told CNN . `` It 's happening ; another Holocaust before our very eyes . There is nothing that we can do . But the world must do something . Please . Please , the world powers must do something for all of these people . '' They are devout Christians , who like many in their village , farmed and lived simple but hard lives off the land . They were taken hostage early Tuesday morning from Hassakeh in northeastern Syria . ISIS abducts scores of Christians in northeastern Syria , groups say . David and his family in Modesto , California , found out about their capture in a devastating phone call . An elderly Syrian man who lived nearby called . He was too sick to leave his home when everyone began fleeing as ISIS fighters stormed the villages in northeast Syria about 30 miles from the Turkish border . `` With his cell phone he called my brother-in-law 's wife and my wife 's sister and told him what has transpired , '' David said . The family has n't heard from the old man since nor any of their captured family members . `` Feeling helpless is overwhelming . We ca n't sleep . It 's devastated us . ... We fear the worst , and we pray for mercy and intervention from God , '' David said . David said ISIS was trying to exact an impossible amount of money , a tax on Christians in Syrian villages and cities they control . The amount was so high -- more than most make in five years -- it was impossible for families to pay , he said . David would not reveal his brother-in-law 's name for fear that ISIS is so media savvy they would single him and his family out if they found out that his brother-in-law is indeed a legal U.S. resident . But he said his brother-in-law is man of deep conviction and could not live comfortably with only part of his family safe in the United States , a country he had come to love . `` He was happy that he was America 's adopted son . He was looking forward to having his son and his son 's family join him and proceeding with a life of prosperity here , '' David said . Now his mission to try to get his remaining family members to America has resulted in him being captured along with them . `` When things started falling apart , he feared for the welfare of his son and son 's family . He could n't very well be here having safe haven here so he went . He is a loving father , and a devout Christian who truly loves God . May God protect him , '' David said . ISIS has attacked numerous minority groups during a bloody campaign to create a vast caliphate across Syria and Iraq under its extreme version of Sharia law . The number of Assyrians estimated to be in captivity has climbed steadily , from an initial estimate of between 70 and 100 people seized earlier this week to 150 as of Wednesday , with women , children and the elderly among them . The London-based Syrian Observatory for Human Rights put the number of Assyrian hostages seized over three days at 220 , in a statement released Thursday . Osama Edward , founder of the Assyrian Human Rights Network , said the number is even higher -- 262 . Activist : ISIS now holds 262 Christians hostages in Syria . The Assyrians are a proud people who 've overcome a lot in their history . They can trace their roots back some 4,000 years to the time of Mesopotamia , considered one of the cradles of civilization and birthplace of writing and literature . While their first religion was Ashurism , Assyrians have been predominantly Christian since the third century . `` How can Syria be Syria without the Assyrians ? '' Edward said . `` We gave the country our name . '' The captured Assyrians have gotten the attention of Rep. Ana Eshoo , a California Democrat , who wrote a letter to President Barack Obama pleading for Washington and the United Nations to try to help secure a safe haven for religious minorities in Syria and Iraq . `` For the past decade we have been witnessing a rapid decline of Syria and Iraq 's Christian communities , '' Eshoo writes . `` The situation for religious minorities in Syria and Iraq remains desperate and soon will be hopeless . We must act now . '' She has proposed more safe havens inside Iraq and Syria for religious minorities , specifically in the Nineveh Plains , as well as adequate humanitarian assistance in refugee camps . CNN 's Steve Almasy contributed to this report .
David brother-in-law went to Los Angeles to be with his son and family as they applied for visas . Hassakeh some 4,000 years has taken hundreds of Democrat hostage . `` We fear the worst , '' David says .