In their 2017 book '' Age of Lone Wolf Terrorism '' , Mark Hamm and Ramon Spaaij regard this shooting as part of a 21st century pattern of " targeting uniformed police and military personnel " by lone wolf terrorists . Writing in the journal CTC Sentinel , Sam Mullins describes this shooting as an instance of " jihadist-inspired violence , " noting that such attacks may be carried out not only by individuals " directed and funded by foreign terrorist organizations " and by " autonomous groups and individuals who are often lacking substantial overseas connections but nevertheless share the same murderous ideology , " but also by " troubled individuals who seem to be driven at least as much by mental illness as by exposure to jihadi propaganda or related media coverage . " Writing in the '' Journal of Strategic Security , '' Martin J. Gallagher , describes this crime and Archer 's assertion of motivation as one of a series of " known lone wolf terrorist attacks in 2016 . " Gallagher , a British police official charged with the investigation of and response to serious crime national crisis events , discusses the " wave " of which this shooting is part as " a tsunami of attacks perpetrated by individuals " who fit the definition of lone wolf terrorist offered by Michael Becker in his 2014 paper , '' Explaining Lone Wolf Target Selection in the United States . '' Gallagher asserts that " there must be an unequivocal acceptance that mental health is a factor in lone wolf terrorism , and that the actions of those who are ill need to be seen as those of a terrorist when appropriate . The Wall Street Journal placed this shooting in the context of a series of ISIS-inspired lone wolf incidents in the United States , including the 2015 San Bernardino attack , pointing out that some 60 individuals were arrested in 2015 in the United States charged with giving support to ISIS ; the '' Journal '' quoted Michael Nacht , a former official with the U.S. Defense Department , now a Professor at the University of California , Berkeley 's Goldman School of Public Policy , who stated that calling on Muslims worldwide to attack non-Muslims is " a very effective ISIS strategy . " The case was revisited by the press in December 2017 when an immigrant from Egypt who was a naturalized citizen of the United states , Ahmed El-Mofty , opened fire on police just outside the Pennsylvania State Capitol Building in Harrisburg , Pennsylvania . The Harrisburg attacker was shot and killed , but the incident sparked a debate about his motivation that was compared with the debate over Archer 's motive
2015 San Bernardino attack
2015 San Bernardino attack
Shooting of Jesse Hartnett