It is nearly a certainty that an intruder knew there were adults in the house who would protect JBR at any cost. Therefore its likely a gun was present, to counter JR's gun. A garrote doesn't cut it.
Remember that the garrote is a multi-purpose weapon. It probably silenced JBR and allowed her to be moved from her bedroom to the basement without disturbing the parents. Quite a feat for 5 bucks and some borrowed wood.
I haven't read that any of the Rs owned a gun, but can't rule it out. I'd have had one if I were them. Even when my kids were that small, I had guns, but kept them in a gun safe.
There are some photos on some other sites that show a strangulation victim who is NOT JB pictured next to JB's photo. The other strangulation victim, ho was said to have been strangled with a scarf, has a large, reddish triangular mark on her throat identical to JB's. I saw it first on Crimeshots, but it also appeared in Ruthee's Pages on ACR (in the JB archives in the "Other People's Pages" section. Ruthee has been dead s a few years now and her site may no longer be available. If I can find it I will post it here.