An imam was killed in a shooting attack outside a mosque in Newark in the U.S. state of New Jersey on Wednesday, as police sought to nab the suspect.

The cleric was shot after 6 a.m. outside the Masjid-Muhammad-Newark Mosque, Newark Public Safety Director Fritz Fragé said in an emailed statement. The victim was taken to a nearby University Hospital and is in critical condition, authorities said.

Hours later, police had no one in custody.

It's unclear what led to the violence and if the imam was targeted. Fragé said the shooting is under investigation and no other information is available. A message seeking more information was left with the mosque.

Gov. Phil Murphy identified the victim as Imam Hassan Sharif. He noted that authorities have no information about who shot him, or why.

"At a time when the Muslim community is concerned by an increase of bias incidents and crimes, I want to assure the Muslim community and people of all faiths that we will do everything in our power to keep all residents safe, especially in or near our houses of worship," Murphy's statement said.

The New Jersey chapter of the Council on American-Islamic Relations, the nation’s largest Muslim civil rights and advocacy organization, said it is gathering information and urged people to contact local police.

"We are deeply concerned about this incident and pray for the speedy recovery of the imam," CAIR-NJ spokesperson Dina Sayedahmed said in a statement.

Complaints submitted after anti-Muslim incidents in the U.S. have tripled over the past few decades, according to a report.