Among other things it has this section describing the different kinds of serial bombers. Not all are “terrorists” as we envision them:

Serial bombmakers vary greatly in skill, motivation and affiliation. Most bombmakers involved with militant groups are, in effect, serial bombers, especially when they are exceptional bombmakers such as those we discussed in the May 17 Security Weekly. These include individuals such as Abu Ibrahim of the Black September Organization, Yahya Ayyash of Hamas or al Qaeda in the Arabian Peninsula’s Ibrahim Hassan Tali al-Asiri. Such individuals typically create hundreds, if not thousands, of innovative explosive devices for their groups’ terrorist operations over a span of many years.

However, not all serial bombmakers are associated with a militant group. There is a long history of individuals who have operated as serial bombers. From 1940 to 1956, George Metesky, who was known in the media as “The Mad Bomber,” deployed 33 IEDs, 22 of which detonated, and injured 15 people. Metesky was angry after being denied disability pay following an injury he sustained while working for Consolidated Edison, Inc. After planting two explosive devices in 1940, Metesky observed a self-imposed moratorium on bombing attacks during World War II. He deployed the bulk of his devices — pipe bombs — from 1951 to 1956. He attacked not only Consolidated Edison, but also theaters, the New York subway system, the New York Public Library, Radio City Music Hall, Grand Central Station and other targets. Metesky was arrested after Consolidated Edison personnel managers identified him based on details he provided in threatening letters.

One of the most famous serial bombers in recent years was Theodore Kaczynski, also known as the “Unabomber.” UNABomb was an FBI case name that stood for “University and Airline Bomber” — Kaczynski’s first targets. From May 1978 until April 1995, Kaczynski deployed 16 IEDs that killed a total of three people and injured 23 more. Like the Metesky case, it was Kaczynski’s writings that allowed him to be identified, though it was Kaczynski’s brother who identified him for authorities. As demonstrated in his manifesto, titled Industrial Society and Its Future (1995), Kaczynski was motivated by a fear of technology. He called for a revolution against modern society’s “industrial-technological system.”

Eric Rudolph first came onto the scene in July 1996 when a bomb he planted in Atlanta’s Centennial Olympic Park detonated during the 1996 Summer Olympics. Rudolph also conducted IED attacks against abortion clinics in Atlanta in 1997 and in Birmingham, Ala., in 1998 and against a gay bar in Atlanta in 1997. Rudolph’s IED attacks killed two and wounded more than 100. Rudolph was motivated by his extreme anti-abortion and anti-homosexual convictions.

Not all serial bombers have intended to kill their targets. From 1994 to 2006, an unidentified bombmaker known by the media as the “Italian Unabomber” planted dozens of small IEDs in various locations in Italy. While many of the IEDs were pipe bombs, the Italian bombmaker also concealed IEDs in cans of tomato paste, cigarette lighters, church votive candles and in items intended to target children, such as bottles of soap bubbles, colored markers and Kinder Eggs. The size of many of these devices suggests that the bombmaker hoped to maim and terrorize his victims but not kill them. A suspect was arrested in the Italian case but was later acquitted, and the case has never been officially solved. Since many serial bombmakers, such as Metesky and Kaczynski, go through periods when they suspend bombmaking activity, it is possible that the Italian bombmaker is still at large and will attack again.

We have to be careful in situations like this to not automatically assign political motives. The whole article is worth your time so check it out.