LOS ANGELES (CBSLA.com) — A leading Southern California terrorism expert said the person behind Monday’s Boston Marathon bombings may not have been particularly skilled at accomplishing such a task.

Three people were killed and more than 140 others injured when two devices detonated on Boylston Street around 2:50 p.m. EST near the marathon’s finish line.

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Brian Jenkins, the senior advisor on terrorism to the president of the RAND Corporation and the director of the National Transportation Security Center at the Mineta Transportation Institute, told KCAL9’s Dave Bryan that he believes the relatively low death toll compared to al Qaeda international attacks may indicate the bomber was not experienced.

“Whoever did this was determined to kill people. I mean, you set up multiple devices at the finishing line of the Boston Marathon. That is just a determination to kill. It suggests that these were probably, and fortunately, crude devices,” said Jenkins.

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Jenkins said whoever carried out the twin blasts falls into one of three categories of domestic or foreign perpetrators.

“It could well be an individual or tiny conspiracy inspired by some foreign ideology like al Qaeda’s ideology. It could be a plot by domestic ideologically motivated extremists. We’ve seen individuals motivated by their own mad ideology carrying out acts of violence,” he said.

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CBS News reported there was no intelligence information in connection to the attack.