Cold, methodical, not wasting shots if he didn't have too; no emotions whatsoever. Apart from some missed shots in the kitchen and two shots to take out Michel who tried to flee. This act of mass-murder has assassination written all over it.
But why did he shoot himself? The lack of emotions rules out any sense of guilt which would justify a suicide.

Why? Why does a straight-a's math post-doc travel a couple of hours to murder an entire farmer family in a frikkin back-water village as Alliance? What is his motive?... Motive
We're trying to bring everything down to the number, but for now no links can be found.

And how did he get here in the first place?...Opportunity

By the way; the assignment to concoct the story about the affair between Dana and Michel Wei, we're well on our way. The local bingo gossip girl (or granny judging by her age) will tell anyone about the affair seed we "planted" in her head, and also mister Saves (Puta to you too :D) is on top of this too; Blue and I went to the bar of the motel where Rico was also having a drink. I sat at the bar dropping some hints in a "drunken" muttering, while Blue was talking to him. So we had him believe there was something going on between the murderer and Dana in notime.

Gullible people everywhere, combined with simple Psych 101 :D

If we stick to that story for a couple more days, all the locals will have picked it up on it, and our job on that front is done.
Which leaves us with all the number stuff which is starting to intrigue me to a point where we're seeing connections between random numbers and "The Number" everywhere; License plate numbers, the serial number of the murder weapon (more on that in a sec btw), the PRICE of a cup of tea in the local cafetaria. (*nod* that price needed capitalizing), the timer on the oven, which got shot at point blank. He must really dislike seventies ovens, although the color was revolting, which might upset even the sanest of people.
We also checked for a relationship between the social security numbers, bank account numbers, longitude and lattitude of the crime scene. But at first sight, there was nothing to be recognized from those unfortunately. So we're still looking for motive.
Val turns out to be some math nerd and she found out some vague stuff about the number, although it had her shaken up, even if only slightly. I'd better leave the mathy stuff to Val to avoid me getting my brain in a twist.
Although Doug would probably have a field-day, if I came in with yet another knotted up brain, at 150$ an hour.

So about that weapon as promised; A Remington 870 shotgun, Sixteen shots. The weapon is now in the custody of the New Jersey state patrol (where our "friendly" has access to all the information we might need) as they had "found" the gun in their area of jurisdiction... *drumroll*.... the street >:)
As I mentioned the serial number of the gun appears as part of "The Number" but also it appears in the inventory list of the 24th precinct in NY. Or at least it did until it went missing some time ago. Because guns go missing on a regular basis of course...

Another lead to check out, how Wei got hold of the gun... means