As Dzhokhar Tsarnaev’s friends have maintained, there was nothing about the Boston marathon bombing suspect’s actions or behavior leading up to the last month’s attack that authorities have deduced as red flags. After a month of intensive investigation, officials are still piecing together the lives of the Tsarnaev brothers, but have so far come up with completely different psychological profiles, according to those familiar with the case. In contrast to Tsarnaev, who frequented jihadi websites and fits the description of a “homegrown” terrorist, Dzhokhar’s actions are more in line with that of a run-of-the-mill criminal. Even if he was only radicalized by his brother at the very last minute, that doesn’t explain why he helped kill so many people without showing any mercy. The latest insight about Dzhokhar exposes limitations in investigators’ attempts to prevent future acts of terrorism.