Police in Northern Ireland arrested a Sudanese man on Tuesday following a knife attack that left one person in serious condition. 

Video of the attack was posted online, which prompted calls for a protest. Police are asking citizens to remain calm, Reuters reported. British Prime Minister Keir Starmer called the attack "sickening." The incident isn't being treated as an act of terrorism. 

The attack follows soon after a United Kingdom stabbing victim, Henry Nowak, was handcuffed by police after his attacker, a Sikh man, falsely claimed Nowak had been racist toward him. Nowak died from his injuries after police initially appeared to dismiss his statements that he'd been stabbed. 

Police said the victim in Tuesday's "brutal" stabbing, which was done with a kitchen knife, was in his 40s and suffered significant injuries to his eyes, face and back. Video posted online appears to show the attacker attempting to behead the victim. Members of the public tried to fight off the attacker before police arrived. 

Police Service of Northern Ireland Chief Constable Jon Boutcher said the suspect is believed to have traveled from Sudan to Belfast via Paris in February 2023. Once in Belfast, he immediately claimed asylum and was given leave to remain in the UK in September 2023, the Daily Mail reported. 

The suspect has been detained on suspicion of attempted murder.