Updated

San Diego's homeless population is on edge after four attacks on transients in four days, two of them fatal.

Police are seeking someone they now identify as the sole suspect, a man seen on convenience store surveillance video wearing a cap, jacket and backpack.

In the latest of the attacks, a 23-year-old man was seriously injured Wednesday and is not expected to survive his upper-body injuries after being attacked.

A news release said the latest victim was set on fire, though Capt. David Nisleit said earlier that a witness pulled away a burning cloth that the attacker had placed on the victim before fleeing.

As in previous attacks the victim was sleeping in the early morning hours when the assailant approached.