A PSNI road policing officer flags down oncoming drivers during a random drink driving checkpoint in Belfast, Northern Ireland, in this file photo from Dec. 21, 2016. Liam McBurney/PA WireThe Police Service of Northern Ireland (PSNI) said that a Sudanese man has been arrested on suspicion of attempted murder after a knife attack in Belfast left another man seriously injured in what authorities have described as a “critical incident.”In the footage, shared widely online, a black male is seen repeatedly stabbing a blood-drenched white man, cutting into his head and eyes and shouting in what appears to be a foreign language as horrified members of the public shout for help while screaming that the attacker is trying to “cut his head off.”