We just got a bit more information about the final break in this case, how and who found the suspect. According to the Boston Police Commissioner, a man in a house in Watertown came out of his house for the first time this afternoon after authorities said people could safely come out of their homes. He saw blood on the cover of his boat (perhaps a tarp or a winter shrink wrap). He approached the boat and looked in and saw a man covered in blood inside the boat. He rushed back into the house and called the police.
Key point is that the witness/tipster made actual eye contact with the suspect, and one would imagine vice versa. So not just that he saw something that looked odd or different. He saw the man himself.
