Authorities are seeking to identify and speak with a man seen in the vicinity of a shooting that left a Concord couple dead. Investigators on Tuesday released a sketch of a man they called a person of interest in the case. They described him as a clean-shaven white man in his late 20s or early 30s, approximately 5 feet, 10 inches tall, with short brown hair. The man was seen near the scene wearing a dark blue jacket with khaki pants and carrying a black backpack. Meanwhile, the reward for information leading to an arrest has increased to $33,500 in large part due to an anonymous donor who promised the money only if someone comes forward in the next 60 days. Information can be submitted anonymously by contacting the Concord Regional Crimeline at (603) 226-3100. Tips can also be submitted online through the Crimeline website at www.concordregionalcrimeline.com, or text message TIP234 and the message to CRIMES (274637). All tips remain anonymous.