Hello, brand new here and just reading up on this thread. I live in MA, I grew up in Everett which is not terribly far from Swampscott. I was born well after this murder happened so take all this with a grain of salt.
After reading the articles and the posts here I have a few opinions on this but they are mostly stabs in the dark.
1) Henry allegedly stated to the DPW members after saying "merry christmas" that he was going to wrap christmas presents. He held up the bag for them to see. This could potentially explain why he went to a secluded place. Perhaps he had purchased the perfume and wrapping paper at the CVS and then walked to a place he knew the person he bought the gift for (I am assuming his mother) would not see it before it was wrapped. This at least could partially explain why he apparently went so far off of his normal route home.
2) Many people here have commented on the $37 which he was carrying that was taken from his wallet. I find this piece of information a bit confusing. How did anyone know or estimate he had just $37 on him if the wallet was empty when it was found? Also this indicates that Henry had more than $37 on his person prior to purchasing the perfume. My guess would be between $40 and $50 since perfume even at CVS aren't that cheap even in 1974. Since LE was able to estimate the amount of money in his wallet that was missing, it can be potentially inferred that someone knew how much money was in his wallet prior to purchasing the perfume.
3) Which leads into my next note on the case...Presumably someone at CVS who sold the perfume to him must have seen roughly how much money was in his wallet, and so therefore any other person that was near Henry at the time of purchase. As many people have stated here before, $37 was close to $200 in today's value in 1974. It therefore can be presumed that Henry had somewhere between $200 and $220 in today's value of cash on hand inside the CVS and that at least one other person was able to determine this by watching him.
4) Several posters on here have discussed the markings on the bat. Many have noted the VI or KM marks, and someone else noted they saw a sword. Another poster also noted the bat had a 31 on it indicating a 31 inch bat. However, although I see a 1, I do not see a 3 in the picture. This bat has been described as a Hank Aaron little league bat. Current little league bat guidelines state that the maximum length of a little league bat (majors) is 33 inches. It is possible this bat was owned by a minor that was likely 15-16 years old at the time. Examining the markings indicates to me that it was intended to be a VI and not a KM. Looking at the picture with the 1 in the upright position seems to indicate the other long marking to the right of the 1 was a poor attempt at scratching out the line for the top of the roman numeral 6. If that is the case, then it's unlikely to be initials or even stand for "varsity 1" but instead would be the number 6, as in the number the player wears that uses the bat. Major leaguers currently do this to their own bats and have been for a very long time. For reference
Uni Watch on the bat knob revolution ‹ Major League Baseball Clubhouse Managers Association "The look of baseball is always changing. But for generations, one thing about the game has stayed the same: Players have had their uniform numbers written on the knobs of their bats."
5) Many people have stated the killer is likely local because no one saw the perpetrator covered in blood and there was a small birthday party taking place not long after the murder in the neighborhood. This is probably a 100% correct assumption because of how the crime took place but one has to keep in mind the area may have been much less densely populated in 1974 and therefore a local may have been able to walk a bit further without being noticed (especially if they knew some routes through the wooded area) on a cold day in December.
Unfortunately this is most of the information that seems pretty solid right now even after all this time. To me it indicates that someone saw the amount of money he had in his wallet. This person had access to a bat and likely wore the number 6 when they played. This person followed Henry to the location and was probably hoping to get him into a secluded spot to rob him or perhaps Henry came upon them unexpectedly and caught them doing something they didn't want him to know. The DPW supervisor stated that after he saw Henry he went inside his small wooden shack so he would not have seen if someone was following him. The person may have known Henry and after initially assaulting him, realized that Henry could identify him. Therefore in a panic he continued to hit Henry until he was sure he was dead so that Henry could not go to the police. It is likely this had to do with the money as the killer left behind the perfume and the wallet. The Varsity and Junior Varsity teams at Swampscott high did not have any players with the initials "KM" (I looked at their yearbook on classmates.com). Unfortunately they did not bother to put a roster with player numbers in the yearbook, so I cannot see who number 6 is (if there was a number 6). The 1975 yearbook does not even have a listing for the baseball team. What is interesting about these yearbooks however is that it lists the street address for all the seniors. Now unsurprisingly but interestingly there are seniors in 1975 that resided at 55 Suffolk Ave. 15 Suffolk Ave. and 1 Suffolk Ave. (No seniors in 1974 resided on Suffolk Ave). What is quite interesting here is that one of them is listed as the "manager" of the 1974 Swampscott High Varsity baseball team in the picture. This is completely circumstantial of course. The individual still lives in MA but no longer in Swampscott.