Police have opened a homicide investigation after a man was stabbed Tuesday night in Kailua.  It happened at 11:45 p.m. and police believe the victim, a man in his 50s, was homeless. He was found with stab wounds on the sidewalk near Cinnamon's Restaurant and taken to the hospital in extremely critical condition, where he died.  Officers from HPD's specialized services division were concentrating their search for the suspect on Uluniu Street, after witnesses say they saw a man running Kaneohe bound from the scene.  Police have a good description from witnesses. The man is in his 20s, 5'2" to 5'4" tall, weighing 140-to-160 pounds with a thin build.  He was wearing a black cap, long-sleeved shirt, dark pants and work boots. This is the second deadly stabbing in two days on Oahu.