Loved ones of 20-year-old Isaac Wilkie posted pictures of him Thursday evening near his home in Harlem.
He was last seen leaving his home on Monday around 7 p.m., but there was a possible sighting of him Thursday morning on a bus on the Upper East Side.
Wilkie is verbal, but likely in distress.
There is particular concern because of the hot weather.
Wilkie is described as about 5'5'' tall, weighing about 220 pounds.
He was last seen wearing blue jeans, a cream-colored shirt and green sneakers.
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