Durham police arrested a man they say assaulted another man and left him in life-threatening condition.The incident occurred on Oct. 6 around 5:40 p.m. in the Ritson Road North and Taunton Road East area. At the scene, officers say they found a male victim suffering from obvious signs of trauma.Investigators say the victim was crossing the street when the suspect allegedly approached him from behind and began assaulting him in an unprovoked attack. The victim was transported to a Toronto-area trauma centre and is currently in life-threatening condition, according to police.Police located and arrested the alleged suspect, Dwayne Wallen, 33, of Oshawa. He was charged with aggravated assault.He was held for a bail hearing.Durham police say the victim and suspect are not known to each other.